草原之王 發表於 2022-12-13 16:11:00

JavaScript中比较字符串的4种方法

<h2 id="strict-equality">严格平等</h2>
<p>要确定字符串是否相等,可以使用严格相等运算符 。如果字符串不同,则返回,如果字符串相同,则返回<code>===</code><code>false&nbsp;</code><code>true</code></p>
<div class="cnblogs_code">
<pre><span style="color: rgba(0, 0, 255, 1)">const</span> s1 = <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">learn</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">;
</span><span style="color: rgba(0, 0, 255, 1)">const</span> s2 = <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">today</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">;

console.log(s1 </span>=== <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">learn</span><span style="color: rgba(128, 0, 0, 1)">'</span>);<span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> true</span>
console.log(s1 === s2);       <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> false</span></pre>
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<p>使用严格相等性比较字符串始终会分析字母的大小写,这意味着大写字母与小字母不同。<code>===</code></p>
<div class="cnblogs_code">
<pre><span style="color: rgba(0, 0, 255, 1)">const</span> s1 = <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">javascript</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">;
</span><span style="color: rgba(0, 0, 255, 1)">const</span> s2 = <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">Javascript</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">;

console.log(s1 </span>=== s2); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> false</span></pre>
</div>
<h2 id="case-insensitive-string-comparison">不区分大小写的字符串比较</h2>
<p>如果你想在JavaScript中对字符串进行不区分大小写的比较,你可以把两个字符串都变成小写,然后使用严格的相等运算符进行比较。</p>
<div class="cnblogs_code">
<pre><span style="color: rgba(0, 0, 255, 1)">const</span> s1 = <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">javascript</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">;
</span><span style="color: rgba(0, 0, 255, 1)">const</span> s2 = <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">Javascript</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">;

console.log(s1.toLowerCase() </span>=== s2.toLowerCase()); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> true</span></pre>
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<h2 id="comparing-the-length-of-javascript-strings">比较 JavaScript 字符串的长度</h2>
<p>如果您需要查找两个字符串中哪一个更长,那么运算符“大于”和“低于”将不太适合您。他们以字母数字顺序逐个比较字符串的字符,并在最后考虑字符串的长度。</p>
<div class="cnblogs_code">
<pre><span style="color: rgba(0, 0, 255, 1)">const</span> s1 = <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">javascript</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">;
</span><span style="color: rgba(0, 0, 255, 1)">const</span> s2 = <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">node.js</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">;

console.log(s1 </span>&gt; s2); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> false</span></pre>
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<p>在 JS 中,每个字符串都有该属性。通过比较不同字符串中此属性的值,我们将了解其中哪个更长。<code>length</code></p>
<div class="cnblogs_code">
<pre><span style="color: rgba(0, 0, 255, 1)">const</span> s1 = <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">javascript</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">;
</span><span style="color: rgba(0, 0, 255, 1)">const</span> s2 = <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">node.js</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">;

console.log(s1.length </span>&gt; s2.length); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> true</span></pre>
</div>
<h2 id="check-if-a-string-contains-another-string">检查一个字符串是否包含另一个字符串</h2>
<p>要检查一个字符串是否是JavaScript中另一个字符串的子字符串,有一个内置函数。请记住,该函数存在于Java中,但在JavaScript中,它被弃用并替换为。<code>includes&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;contains&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;includes</code></p>
<div class="cnblogs_code">
<pre><span style="color: rgba(0, 0, 255, 1)">const</span> s1 = <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">javascript</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">;
</span><span style="color: rgba(0, 0, 255, 1)">const</span> s2 = <span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">python</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)">;

console.log(s1.includes(</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">script</span><span style="color: rgba(128, 0, 0, 1)">'</span>)); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> true</span>
console.log(s2.includes(<span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">script</span><span style="color: rgba(128, 0, 0, 1)">'</span>)); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> false</span>
console.log(s1.contains(<span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">java</span><span style="color: rgba(128, 0, 0, 1)">'</span>))    <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> ERROR! .contains is not a function</span></pre>
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<p>&nbsp;</p>

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