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<!DOCTYPE html>
<html lang="zh-TW">
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<article>
<h2>新標準 ES2021 (ES12)</h2>
<h2 id="15-1">15-1 String.prototype.replaceAll</h2>
<p>
第一個參數可以是正則表達式或是單一字串代表要取代的篩選條件，第二個參數要是取代舊字串的文字。我們現在可以使用
<code>String.prototype.replaceAll</code>
回傳一個將指定文字取代掉的全新字段，不會修改到原參考文字。第一個參數可以是正則表達式或是單一字串代表要取代的篩選條件，第二個參數要是取代舊字串的文字。請看以下範例：
</p>
<pre><code class="language-js">
const p = 'The quick brown fox jumps over the lazy dog. If the dog reacted, was it really lazy?';
console.log(p.replaceAll('dog', 'monkey'));
// Expected output: "The quick brown fox jumps over the lazy monkey. If the monkey reacted, was it really lazy?"
// Global flag required when calling replaceAll with regex
const regex = /Dog/gi;
console.log(p.replaceAll(regex, 'ferret'));
// Expected output: "The quick brown fox jumps over the lazy ferret. If the ferret reacted, was it really lazy?"
</code></pre>
<p>
需要注意的是，如果使用正則，沒有使用修飾符
<code>/g</code>
則會報錯
</p>
<pre><code class="language-js error-code">
const p = 'The quick brown fox jumps over the lazy dog. If the dog reacted, was it really lazy?';
const wrongRegex = /Dog/i;
console.log(p.replaceAll(wrongRegex, 'ferret'));
// Uncaught TypeError: String.prototype.replaceAll called with a non-global RegExp argument at String.replaceAll
</code></pre>
<h3>比較 String.prototype.replace()</h3>
<p>
<code>replace</code>
使用正則表達式做動態取代時比較容易發生非預期錯誤：
</p>
<pre><code class="language-js">
function unsafeRedactName(text, name) {
return text.replace(new RegExp(name, "g"), "[REDACTED]");
}
function safeRedactName(text, name) {
return text.replaceAll(name, "[REDACTED]");
}
const report =
"A hacker called ha.*er used special characters in their name to breach the system.";
console.log(unsafeRedactName(report, "ha.*er")); // "A [REDACTED]s in their name to breach the system."
console.log(safeRedactName(report, "ha.*er")); // "A hacker called [REDACTED] used special characters in their name to breach the system."
</code></pre>
<h3>更加有趣的用法</h3>
<p>
第一個參數傳入空字串可以達成類似分割字段方法：
<code>String.prototype.split()</code>
</p>
<pre><code class="language-js">
"xxx".replaceAll("", "_"); // "_x_x_x_"
</code></pre>
<p></p>
<p>資料來源:</p>
<p>
<a
href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replaceAll"
>
https://developer.mozilla.org/.../replaceAll
</a>
</p>
</article>
</main>
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