goja
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docz/docs/03-demos/31-engines/05_goja.md
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136
docz/docs/03-demos/31-engines/05_goja.md
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---
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title: Go + Goja
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pagination_prev: demos/cli
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pagination_next: demos/clipboard
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---
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Goja is a pure Go implementation of ECMAScript 5.
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The [Standalone scripts](/docs/getting-started/installation/standalone) can be
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parsed and evaluated in a Goja context.
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## Integration Details
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_Initialize Goja_
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Goja does not provide a `global` variable. It can be created in one line:
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```go
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/* initialize */
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vm := goja.New()
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/* goja does not expose a standard "global" by default */
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// highlight-next-line
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v, err := vm.RunString("var global = (function(){ return this; }).call(null);")
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```
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_Load SheetJS Scripts_
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The shim and main libraries can be loaded by reading the scripts from the file
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system and evaluating in the Goja context:
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```go
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func safe_run_file(vm *goja.Runtime, file string) {
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data, err := ioutil.ReadFile(file)
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if err != nil { panic(err) }
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src := string(data)
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_, err = vm.RunString(src)
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if err != nil { panic(err) }
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}
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// ...
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safe_run_file(vm, "shim.min.js")
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safe_run_file(vm, "xlsx.full.min.js")
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```
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To confirm the library is loaded, `XLSX.version` can be inspected:
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```go
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/* get version string */
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v, err := vm.RunString("XLSX.version")
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fmt.Printf("SheetJS library version %s\n", v)
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```
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### Reading Files
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Files can be read into `[]byte`:
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```go
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/* read file */
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data, _ := ioutil.ReadFile("sheetjs.xlsx")
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```
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`[]byte` should be converted to an `ArrayBuffer` from Go:
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```go
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/* load into engine */
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vm.Set("buf", vm.ToValue(vm.NewArrayBuffer(data)))
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/* parse */
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wb, _ = vm.RunString("wb = XLSX.read(buf, {type:'buffer'});")
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```
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### Writing Files
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`"base64"` strings can be passed from the JS context to Go code:
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```go
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/* write to Base64 string */
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b64str, _ := vm.RunString("XLSX.write(wb, {type:'base64', bookType:'xlsx'})")
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/* pull data back into Go and write to file */
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buf, _ := base64.StdEncoding.DecodeString(b64str.String())
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_ = ioutil.WriteFile("sheetjs.xlsx", buf, 0644)
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```
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## Complete Example
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:::note
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This demo was tested on 2023 February 14.
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:::
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0) Create a module and install dependencies:
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```bash
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mkdir SheetGoja
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cd SheetGoja
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go mod init SheetGoja
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go get github.com/dop251/goja
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```
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1) Download the standalone script, shim and test file:
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<ul>
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<li><a href={`https://cdn.sheetjs.com/xlsx-latest/package/dist/xlsx.full.min.js`}>xlsx.full.min.js</a></li>
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<li><a href={`https://cdn.sheetjs.com/xlsx-latest/package/dist/shim.min.js`}>shim.min.js</a></li>
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<li><a href="https://sheetjs.com/pres.numbers">pres.numbers</a></li>
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</ul>
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```bash
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curl -LO https://cdn.sheetjs.com/xlsx-latest/package/dist/shim.min.js
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curl -LO https://cdn.sheetjs.com/xlsx-latest/package/dist/xlsx.full.min.js
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curl -LO https://sheetjs.com/pres.numbers
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```
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2) Download [`SheetGoja.go`](pathname:///goja/SheetGoja.go):
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```bash
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curl -LO https://docs.sheetjs.com/goja/SheetGoja.go
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```
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3) Build standalone `SheetGoja` binary:
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```bash
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go build SheetGoja.go
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```
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4) Run the demo:
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```bash
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./SheetGoja pres.numbers
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```
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If the program succeeded, the CSV contents will be printed to console and the
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file `sheetjsw.xlsb` will be created. That file can be opened with Excel.
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@ -67,145 +67,9 @@ The demo includes examples in C and Perl.
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### Goja
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Goja is a pure Go implementation of ECMAScript 5. It supports the standalone
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scripts out of the box.
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**Reading data**
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Files can be read into `[]byte`:
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```go
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/* read file */
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data, _ := ioutil.ReadFile("sheetjs.xlsx")
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```
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`[]byte` should be converted to an `ArrayBuffer` from Go:
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```go
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/* load into engine */
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vm.Set("buf", vm.ToValue(vm.NewArrayBuffer(data)))
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/* parse */
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wb, _ = vm.RunString("wb = XLSX.read(buf, {type:'buffer'});")
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```
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**Writing data**
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`"base64"` strings can be decoded in Go:
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```go
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/* write to Base64 string */
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b64str, _ := vm.RunString("XLSX.write(wb, {type:'base64', bookType:'xlsx'})")
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/* pull data back into Go and write to file */
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buf, _ := base64.StdEncoding.DecodeString(b64str.String())
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_ = ioutil.WriteFile("sheetjs.xlsx", buf, 0644)
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```
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<details><summary><b>Complete Example</b> (click to show)</summary>
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0) Install Go
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1) Create a `go.mod` file and install dependencies:
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```bash
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go mod init SheetGoja
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go get github.com/dop251/goja
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```
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2) Download the standalone script and the shim:
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<ul>
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<li><a href={`https://cdn.sheetjs.com/xlsx-latest/package/dist/xlsx.full.min.js`}>xlsx.full.min.js</a></li>
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<li><a href={`https://cdn.sheetjs.com/xlsx-latest/package/dist/shim.min.js`}>shim.min.js</a></li>
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</ul>
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3) Save the following code to `SheetGoja.go`:
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```go title="SheetGoja.go"
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package main
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import (
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b64 "encoding/base64"
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"fmt"
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"os"
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"io/ioutil"
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"github.com/dop251/goja"
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)
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func safe_run_file(vm *goja.Runtime, file string) {
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data, err := ioutil.ReadFile(file)
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if err != nil { panic(err) }
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src := string(data)
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_, err = vm.RunString(src)
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if err != nil { panic(err) }
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}
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func eval_string(vm *goja.Runtime, cmd string) goja.Value {
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v, err := vm.RunString(cmd)
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if err != nil { panic(err) }
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return v
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}
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func write_type(vm *goja.Runtime, t string) {
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b64str := eval_string(vm, "XLSX.write(wb, {type:'base64', bookType:'" + t + "'})")
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buf, err := b64.StdEncoding.DecodeString(b64str.String());
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if err != nil { panic(err) }
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err = ioutil.WriteFile("sheetjsg." + t, buf, 0644)
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if err != nil { panic(err) }
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}
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func main() {
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vm := goja.New()
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/* initialize */
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eval_string(vm, "if(typeof global == 'undefined') global = (function(){ return this; }).call(null);")
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/* load library */
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safe_run_file(vm, "shim.min.js")
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safe_run_file(vm, "xlsx.full.min.js")
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/* get version string */
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v := eval_string(vm, "XLSX.version")
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fmt.Printf("SheetJS library version %s\n", v)
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/* read file */
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data, err := ioutil.ReadFile(os.Args[1])
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if err != nil { panic(err) }
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vm.Set("buf", vm.ToValue(vm.NewArrayBuffer(data)))
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fmt.Printf("Loaded file %s\n", os.Args[1])
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/* parse workbook */
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eval_string(vm, "wb = XLSX.read(buf, {type:'buffer'});")
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fmt.Printf("Parsed %s\n", os.Args[1])
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eval_string(vm, "ws = wb.Sheets[wb.SheetNames[0]]")
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fmt.Printf("Grabbed %s\n", os.Args[1])
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/* print CSV */
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csv := eval_string(vm, "XLSX.utils.sheet_to_csv(ws)")
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fmt.Printf("%s\n", csv)
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/* write file */
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write_type(vm, "csv")
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}
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```
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4) Build `SheetGoja`:
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```bash
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go build SheetGoja.go
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```
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For testing, download <https://sheetjs.com/pres.numbers> and run
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```bash
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./SheetGoja pres.numbers
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```
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This will print the contents as a CSV to screen AND write to `sheetjsg.csv`
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</details>
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Goja is a pure Go implementation of ECMAScript 5.
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This demo has been moved [to a dedicated page](/docs/demos/engines/goja).
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### Hermes
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61
docz/static/goja/SheetGoja.go
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61
docz/static/goja/SheetGoja.go
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/* SheetGoja (C) SheetJS LLC -- https://sheetjs.com */
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package main
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import (
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b64 "encoding/base64"
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"fmt"
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"os"
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"io/ioutil"
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"github.com/dop251/goja"
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)
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func safe_run_file(vm *goja.Runtime, file string) {
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data, err := ioutil.ReadFile(file)
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if err != nil { panic(err) }
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_, err = vm.RunString(string(data))
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if err != nil { panic(err) }
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}
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func eval_string(vm *goja.Runtime, cmd string) goja.Value {
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v, err := vm.RunString(cmd)
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if err != nil { panic(err) }
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return v
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}
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func write_type(vm *goja.Runtime, t string) {
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b64str := eval_string(vm, "XLSX.write(wb, {type:'base64', bookType:'" + t + "'})")
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buf, err := b64.StdEncoding.DecodeString(b64str.String());
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if err != nil { panic(err) }
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err = ioutil.WriteFile("sheetjsw." + t, buf, 0644)
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if err != nil { panic(err) }
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}
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func main() {
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/* initialize */
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vm := goja.New()
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eval_string(vm, "var global = (function(){ return this; }).call(null);")
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/* load library */
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safe_run_file(vm, "shim.min.js")
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safe_run_file(vm, "xlsx.full.min.js")
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/* get version string */
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v := eval_string(vm, "XLSX.version")
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fmt.Printf("SheetJS library version %s\n", v)
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/* read file */
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data, err := ioutil.ReadFile(os.Args[1])
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if err != nil { panic(err) }
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vm.Set("buf", vm.ToValue(vm.NewArrayBuffer(data)))
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/* parse workbook */
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eval_string(vm, "wb = XLSX.read(buf, {type:'buffer'});")
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eval_string(vm, "ws = wb.Sheets[wb.SheetNames[0]]")
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/* print CSV */
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csv := eval_string(vm, "XLSX.utils.sheet_to_csv(ws)")
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fmt.Printf("%s\n", csv)
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/* write file */
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write_type(vm, "xlsb")
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}
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