vue3 计算字符串的高度与宽度，通过Canvas API的TextMetrics 接口来实现
1、先上一张官方的说明图：
地址：https://developer.mozilla.org/zh-CN/docs/Web/API/TextMetrics
官方实例：
<canvas id="canvas" width="550" height="500"></canvas>
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
const baselinesAboveAlphabetic = ["fontBoundingBoxAscent","actualBoundingBoxAscent","emHeightAscent","hangingBaseline",
];
const baselinesBelowAlphabetic = ["ideographicBaseline","emHeightDescent","actualBoundingBoxDescent","fontBoundingBoxDescent",
];
const baselines = [...baselinesAboveAlphabetic, ...baselinesBelowAlphabetic];
ctx.font = "25px serif";
ctx.strokeStyle = "red";
baselines.forEach((baseline, index) => {const text = `Abcdefghijklmnop (${baseline})`;const textMetrics = ctx.measureText(text);const y = 50 + index * 50;ctx.beginPath();ctx.fillText(text, 0, y);let lineY = y - Math.abs(textMetrics[baseline]);if (baselinesBelowAlphabetic.includes(baseline)) {lineY = y + Math.abs(textMetrics[baseline]);}ctx.moveTo(0, lineY);ctx.lineTo(550, lineY);ctx.stroke();
});
运行效果说明：
2、然后我们用vue3做一个小的demo测试下(以下代码修改于baidu ai):
<template><div><canvas ref="canvas" style="display: none;"></canvas><p>Text height: {{ textHeight }}px</p></div></template><script setup>import { ref, onMounted, watch } from 'vue';const text = ref('您好世界');const textHeight = ref(0);const canvas = ref(null);onMounted(() => {measureTextHeight();});watch(text, measureTextHeight);function measureTextHeight() {const ctx = canvas.value.getContext('2d');ctx.font = '20px Microsoft Yahei';const metrics = ctx.measureText(text.value);let width = metrics.width;let height = metrics.actualBoundingBoxAscent + metrics.actualBoundingBoxDescent;textHeight.value = height;return { width, height };}</script>运行结果：
说明：这种方法canvas可以精确的计算出，当然也有通过动态创建div，然后通过div的高度来计算，此方法测试发现不是很精确。当然实际开发过程中要进行适当调整。
代码也帖出来：
function getWordHeight(fontSize: string, fontFamily: string, sTextStr: string) {console.log('getWordHeight:', sTextStr);let newDiv = document.createElement('div');newDiv.style.fontSize = fontSize + 'px';newDiv.style.fontFamily = fontFamily;newDiv.innerText = sTextStr;// 将新 div 插入文档流中，这样才能计算出其高度和宽度document.body.appendChild(newDiv);// 计算新 div 的高度和宽度let height = newDiv.offsetHeight; //clientHeightlet width = newDiv.offsetWidth; //clientWidth// 从文档流中移除新 divnewDiv.remove();return { width, height };}