padStart() 在 IE11 中不工作

Question

我正在使用 angularjs 1.7.2 和 kendo ui scheduler。除了涉及 IE 11 中的 padStart() 部分外，所有路由在几乎所有浏览器中都运行良好。当使用 padStart 代码时，会出现此错误

TypeError: 对象不支持属性或方法 'padStart'

let ret = '#' + ((r << 16) + (g << 8) + b).toString(16).padStart(6, '0');

有没有办法我们可以处理这个问题或实现 padStart

的替代方法

Answer 1

IE 11 不支持此功能。请看这里：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/padStart#Browser_compatibility

您正在寻找的是填充浏览器缺失功能的 polyfill。以下代码也取自 developer.mozilla.org 会对您有所帮助：

// https://github.com/behnammodi/polyfill/blob/master/string.polyfill.js
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/padStart
if (!String.prototype.padStart) {
    String.prototype.padStart = function padStart(targetLength,padString) {
        targetLength = targetLength>>0; //truncate if number or convert non-number to 0;
        padString = String((typeof padString !== 'undefined' ? padString : ' '));
        if (this.length > targetLength) {
            return String(this);
        }
        else {
            targetLength = targetLength-this.length;
            if (targetLength > padString.length) {
                padString += padString.repeat(targetLength/padString.length); //append to original to ensure we are longer than needed
            }
            return padString.slice(0,targetLength) + String(this);
        }
    };
}

编辑：如评论中所述，@Plaute 还需要对函数 repeat 进行 polyfill，可在此处找到：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat

或包含此代码段：

if (!String.prototype.repeat) {
  String.prototype.repeat = function(count) {
    'use strict';
    if (this == null) {
      throw new TypeError('can\'t convert ' + this + ' to object');
    }
    var str = '' + this;
    count = +count;
    if (count != count) {
      count = 0;
    }
    if (count < 0) {
      throw new RangeError('repeat count must be non-negative');
    }
    if (count == Infinity) {
      throw new RangeError('repeat count must be less than infinity');
    }
    count = Math.floor(count);
    if (str.length == 0 || count == 0) {
      return '';
    }
    // Ensuring count is a 31-bit integer allows us to heavily optimize the
    // main part. But anyway, most current (August 2014) browsers can't handle
    // strings 1 << 28 chars or longer, so:
    if (str.length * count >= 1 << 28) {
      throw new RangeError('repeat count must not overflow maximum string size');
    }
    var maxCount = str.length * count;
    count = Math.floor(Math.log(count) / Math.log(2));
    while (count) {
       str += str;
       count--;
    }
    str += str.substring(0, maxCount - str.length);
    return str;
  }
}

或者，要解决 String.prototype.repeat 依赖项，请使用以下行：

padString += Array.apply(null, Array(targetLength)).map(function(){ return padString; }).join("");

padStart() 在 IE11 中不工作

padStart() not working in IE11

javascript

cross-browser

angularjs

internet-explorer-11