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HomeBackend DevelopmentPHP Tutorialjs下函数般调用正则的方法附代码_PHP

曾经 ECMAScript 4 建议指出这个功能将会增加到 ES4 规范中,但后来的在 ES4-discuss mailing list 的讨论中,这个建议可能被废除。

然而,你可以通过增加 call 和 apply 方法到 RegExp.prototype 中类似的现实这些方法。既有助于功能设计,又可实现对函数和正则表达式均有效的隐藏类型(duck-typed )代码。因此,让我们增加这些方法。

RegExp.prototype.call = function (context, str) {
    return this.exec(str);
};
RegExp.prototype.apply = function (context, args) {
    return this.exec(args[0]);
};注意上面的两个方法完全忽略 context 参数,你可以提交 null 或者 任何其他作为 context 的对象,并且你将会类似的得到正则 exec 方法的返回值。使用上面的方法,无论在什么情况下,使我们正常地使用正则表达式和函数变得容易得多。一些很明显的例子,比如这些在 JavaScript 1.6 的数组迭代中很有用。下面的 filter, every, some, 和 map 方法的执行可以跨浏览器。

if (!Array.prototype.filter) {
    // 返回一个数组,如果提供的过滤函数返回 true,则返回存在的数组中的元素。
    Array.prototype.filter = function (func, context) {
        var results = [];
        for (var i = 0; i             if (i in this && func.call(context, this[i], i, this))
            results.push(this[i]);
        }
        return results;
    };
}

if (!Array.prototype.every) {
    // 返回 true ,如果数组中的每个元素满足提供的测试函数。
    Array.prototype.every = function (func, context) {
        for (var i = 0; i             if (i in this && !func.call(context, this[i], i, this))
            return false;
        }
        return true;
    };
}

if (!Array.prototype.some) {
    // 返回 true,如果数组中至少有一个元素满足提供的测试函数。
    Array.prototype.some = function (func, context) {
        for (var i = 0; i             if (i in this && func.call(context, this[i], i, this))
            return true;
        }
        return false;
    };
}

if (!Array.prototype.map) {
    // 返回一个数组,现有数组中的每个元素调用提供的函数的返回值。
    Array.prototype.map = function (func, context) {
        var results = [];
        for (var i = 0; i             if (i in this)
            results[i] = func.call(context, this[i], i, this);
        }
        return results;
    };
}因为exec 方法返回数组或 null 值,并会恰当的类型转换为 true 和 false,上面的代码允许我们像这样使用:["a","b","ab","ba"].filter(/^a/),返回所有以“a”开始的值:["a","ab"]。

确实,在 Firefox 中已经实现了 Array.prototype.filter ,由于 exec 的间接调用已经在该浏览器中起作用了。但是如果 filter 没有添加 RegExp.prototype.call 方法,却无法跨浏览器执行。

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