--- title: Svelte pagination_prev: demos/index pagination_next: demos/mobile/index sidebar_position: 4 --- [Svelte](https://svelte.dev/) is a JS library for building user interfaces. This demo tries to cover common Svelte data flow ideas and strategies. Svelte familiarity is assumed. Other demos cover general Svelte deployments, including: - [iOS applications powered by CapacitorJS](/docs/demos/mobile/capacitor) - [Desktop application powered by Wails](/docs/demos/desktop/wails) ## Installation [The "Frameworks" section](/docs/getting-started/installation/frameworks) covers installation with Yarn and other package managers. The library can be imported directly from Svelte files with: ```js import { read, utils, writeFile } from 'xlsx'; ``` ## Internal State The various SheetJS APIs work with various data shapes. The preferred state depends on the application. ### Array of Objects Typically, some users will create a spreadsheet with source data that should be loaded into the site. This sheet will have known columns. For example, our [presidents sheet](https://sheetjs.com/pres.xlsx) has "Name" / "Index" columns: ![`pres.xlsx` data](pathname:///pres.png) This naturally maps to an array of typed objects, as in the TS example below: ```ts import { read, utils } from 'xlsx'; interface President { Name: string; Index: number; } const f = await (await fetch("https://sheetjs.com/pres.xlsx")).arrayBuffer(); const wb = read(f); const data = utils.sheet_to_json<President>(wb.Sheets[wb.SheetNames[0]]); console.log(data); ``` `data` will be an array of objects: ```js [ { Name: "Bill Clinton", Index: 42 }, { Name: "GeorgeW Bush", Index: 43 }, { Name: "Barack Obama", Index: 44 }, { Name: "Donald Trump", Index: 45 }, { Name: "Joseph Biden", Index: 46 } ] ``` A component will typically map over the data. The following example generates a TABLE with a row for each President: ```html title="src/SheetJSSvelteAoO.svelte" <script> import { onMount } from 'svelte'; import { read, utils, writeFileXLSX } from 'xlsx'; /* the component state is an array of presidents */ let pres = []; /* Fetch and update the state once */ onMount(async() => { const f = await (await fetch("https://sheetjs.com/pres.xlsx")).arrayBuffer(); const wb = read(f); // parse the array buffer const ws = wb.Sheets[wb.SheetNames[0]]; // get the first worksheet // highlight-start pres = utils.sheet_to_json(ws); // generate objects and update state // highlight-end }); /* get state data and export to XLSX */ function exportFile() { // highlight-next-line const ws = utils.json_to_sheet(pres); const wb = utils.book_new(); utils.book_append_sheet(wb, ws, "Data"); writeFileXLSX(wb, "SheetJSSvelteAoO.xlsx"); } </script> <main> <table><thead><th>Name</th><th>Index</th></thead><tbody> <!-- highlight-start --> {#each pres as p}<tr> <td>{p.Name}</td> <td>{p.Index}</td> </tr>{/each} <!-- highlight-end --> </tbody><tfoot><td colSpan={2}> <button on:click={exportFile}>Export XLSX</button> </td></tfoot></table> </main> ``` ### HTML The main disadvantage of the Array of Objects approach is the specific nature of the columns. For more general use, passing around an Array of Arrays works. However, this does not handle merge cells well! The `sheet_to_html` function generates HTML that is aware of merges and other worksheet features. Svelte `@html` tag allows raw HTML strings: ```html title="src/SheetJSSvelteHTML.svelte" <script> import { onMount } from 'svelte'; import { read, utils, writeFileXLSX } from 'xlsx'; let html = ""; let tbl; /* Fetch and update the state once */ onMount(async() => { const f = await (await fetch("https://sheetjs.com/pres.xlsx")).arrayBuffer(); const wb = read(f); // parse the array buffer const ws = wb.Sheets[wb.SheetNames[0]]; // get the first worksheet // highlight-start html = utils.sheet_to_html(ws); // generate HTML and update state // highlight-end }); /* get state data and export to XLSX */ function exportFile() { // highlight-start const elt = tbl.getElementsByTagName("TABLE")[0]; const wb = utils.table_to_book(elt); // highlight-end writeFileXLSX(wb, "SheetJSSvelteHTML.xlsx"); } </script> <main> <button on:click={exportFile}>Export XLSX</button> <!-- highlight-start --> <div bind:this={tbl}>{@html html}</div> <!-- highlight-end --> </main> ```