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有时候我们在使用Canvas绘制一段文本时,会需要通过measureText()方法获取文本的宽度,例如:

创建canvas标签

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

获取一段文本的宽度

var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');

var text = ctx.measureText('foo'); // TextMetrics object
text.width; // 16;

如上所示,measureText返回的其实是一个TextMetrics对象,它包含了文本的宽度,MDN上的解释如下:

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

在微信小程序现在的版本(v2.13.7)中,小程序的canvas还不支持measureText,所以我自己写了个类似于measureText方法,通过canvas获取文本的宽度,方法如下:

function measureText (text, fontSize=10) {
    text = String(text);
    var text = text.split('');
    var width = 0;
    text.forEach(function(item) {
        if (/[a-zA-Z]/.test(item)) {
            width += 7;
        } else if (/[0-9]/.test(item)) {
            width += 5.5;
        } else if (/\./.test(item)) {
            width += 2.7;
        } else if (/-/.test(item)) {
            width += 3.25;
        } else if (/[\u4e00-\u9fa5]/.test(item)) {  //中文匹配
            width += 10;
        } else if (/\(|\)/.test(item)) {
            width += 3.73;
        } else if (/\s/.test(item)) {
            width += 2.5;
        } else if (/%/.test(item)) {
            width += 8;
        } else {
            width += 10;
        }
    });
    return width * fontSize / 10;
}

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Everyday life is like programming, I guess.