--- title: Svelte --- [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](./mobile#capacitorjs) - [Desktop application powered by Wails](./desktop#wails) ## Installation [The "Frameworks" section](../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(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"
{#each pres as p}{/each}
NameIndex
{p.Name} {p.Index}
``` ### 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"
{@html html}
```