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55 lines
2.2 KiB
HTML
55 lines
2.2 KiB
HTML
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<p>增强所有函数，使其具有 <code>callPolyfill</code> 方法。该方法接受一个对象 <code>obj</code> 作为第一个参数，以及任意数量的附加参数。<code>obj</code> 成为函数的 <code>this</code> 上下文。附加参数将传递给该函数（即 <code>callPolyfill</code> 方法所属的函数）。</p>
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<p>例如，如果有以下函数：</p>
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<pre>
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function tax(price, taxRate) {
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const totalCost = price * (1 + taxRate);
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console.log(`The cost of ${this.item} is ${totalCost}`);
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}
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</pre>
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<p>调用 <code>tax(10, 0.1)</code> 将输出 <code>"The cost of undefined is 11"</code> 。这是因为 <code>this</code> 上下文未定义。</p>
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<p>然而，调用 <code>tax.callPolyfill({item: "salad"}, 10, 0.1)</code> 将输出 <code>"The cost of salad is 11"</code> 。<code>this</code> 上下文被正确设置，函数输出了适当的结果。</p>
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<p>请在不使用内置的 <code>Function.call</code> 方法的情况下解决这个问题。</p>
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<p> </p>
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<p><strong class="example">示例 1：</strong></p>
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<pre>
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<strong>输入：</strong>
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fn = function add(b) {
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return this.a + b;
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}
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args = [{"a": 5}, 7]
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<b>输出：</b>12
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<strong>解释：</strong>
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fn.callPolyfill({"a": 5}, 7); // 12
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<code>callPolyfill </code>将 "this" 上下文设置为 <code>{"a": 5} </code>，并将 7 作为参数传递。
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</pre>
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<p><strong class="example">示例 2：</strong></p>
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<pre>
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<b>输入：</b>
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fn = function tax(price, taxRate) {
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return `The cost of the ${this.item} is ${price * taxRate}`;
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}
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args = [{"item": "burger"}, 10, 1,1]
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<b>输出：</b>"The cost of the burger is 11"
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<b>解释：</b><code>callPolyfill </code>将 "this" 上下文设置为 <code>{"item": "burger"} </code>，并将 10 和 1.1 作为附加参数传递。
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</pre>
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<p> </p>
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<p><strong>提示：</strong></p>
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<ul style="list-style-type:square;">
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<li><code><font face="monospace">typeof args[0] == 'object' and args[0] != null</font></code></li>
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<li><code>1 <= args.length <= 100</code></li>
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<li><code>2 <= JSON.stringify(args[0]).length <= 10<sup>5</sup></code></li>
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</ul>
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