Svelte

@mochart/svelte wraps @mochart/core in Svelte 5 components. Config and data changes get mochart's staged animations for free — axis expansion, value change, axis contraction, and gapless stacked transitions — no extra wiring needed.

Install

npm install @mochart/svelte @mochart/core svelte

The optional stylesheet

If your app uses a global CSS reset (Tailwind's preflight, a normalize.css-style reset), also import the core package's optional stylesheet — it re-asserts the browser defaults the chart's tooltip and message overlays rely on, and never overrides the chart's own styling:

import '@mochart/core/mochart.css';

Quick start

DefaultChart is the simplest entry point — give it a raw config and a plain array-of-objects dataset:

<script>
  import { DefaultChart } from '@mochart/svelte';

  const config = {
    title: { text: 'Revenue' },
    categoryAxis: { property: 'month', type: 'string', scale: 'ordinal' },
    seriesDefaults: { renderer: 'bar' },
    series: [{ property: 'revenue', title: 'Revenue' }]
  };

  const data = [
    { month: 'Jan', revenue: 10 },
    { month: 'Feb', revenue: 20 }
  ];
</script>

<DefaultChart {config} {data} width={640} height={400} />

Chart is the lower-level component for hosts that manage config enhancement and data providers themselves:

<script>
  import { enhanceConfig, ArrayOfObjectsDataProvider } from '@mochart/core';
  import { Chart } from '@mochart/svelte';

  const mochartConfig = enhanceConfig(config);
  const dataProvider = new ArrayOfObjectsDataProvider(data, 'month');
</script>

<Chart {mochartConfig} {dataProvider} width={640} height={400} />

Sizing

width and height are optional. The component renders a container div the chart mounts into; whichever dimension you omit tracks that div's size via ResizeObserver. Size the div with the class/style props and the chart follows it:

<Chart {mochartConfig} {dataProvider} style="width: 100%; height: 400px" />

Explicit width/height props win over conflicting style values.

The optional dataTestId prop sets a data-testid attribute on the same container div, for test selectors.

When the data changes

Config and data changes are detected by reference identity: the chart compares the props it receives, not their contents. $state's deep reactivity updates your own markup after an in-place push, but the chart still sees the same array — reassign instead of mutate:

let data = $state(initialData);

// ✓ a new array — the chart animates to it
data = [...data, { month: 'Mar', revenue: 30 }];

// ✗ invisible to the chart — same array identity
data.push({ month: 'Mar', revenue: 30 });

The same rule applies to config on DefaultChart and to mochartConfig/dataProvider on Chart — pass a new object (or provider) to change them.

For hosts that do mutate data in place, bind:this exposes the core refresh() escape hatch — it re-reads the current config/data, re-indexing the built-in providers:

<script>
  let chart;

  function addRow(row) {
    data.push(row);
    chart.refresh();
  }
</script>

<DefaultChart bind:this={chart} {config} {data} />

Callbacks and states

Both components accept the chart callbacks under their core names (onChartClick, onFocus, onSliceClick, …) and a placeholder prop per state. Each placeholder prop takes a Svelte component that receives the chart state context (width, height, error, …) as props and is rendered while the chart is in that state. Both components also accept loading and error to force the loading or error state.

Every prop, with its type and its core counterpart, is listed in Framework props.

Controlled state

Focus and legend filtering are chart-managed by default, but each piece of that state has a matching prop that takes over while it is set (not undefined): focusedCategoryIndex (-1 = none), focusedSeriesId and focusedValueAxisId (null = none), and filteredSeriesIds (a map of series id → true = filtered out). Pass back what onFocus and onSeriesFilter report to keep focus and filtering in sync across several charts (the round-trip is shown in Controlled focus and filtering); leave a prop undefined to let the chart keep managing that piece itself.

See it in action

The Svelte demo gallery is a full application built on @mochart/svelte (Svelte 5 runes router); its source lives in packages/mochart-demo-svelte.