The CanvasRenderingContext2D.measureText() method returns a TextMetrics object that contains information about the measured text (such as its width, for example).

text

The text string to measure.

A TextMetrics object.

Given this <canvas> element:

<canvas id="canvas"></canvas>

… you can get a TextMetrics object using the following code:

const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");

let text = ctx.measureText("Hello world");
console.log(text.width); // 56;

• The interface defining this method: CanvasRenderingContext2D
• TextMetrics