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javascript - 替换 document.getElementById ("demoID").style.color = "blue"是否安全?与 demoID.style.color = "blue";

转载 作者:行者123 更新时间:2023-11-30 19:01:04 27 4
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考虑这段 JavaScript 代码 here (在浏览器 JavaScript 中):

  var x = document.getElementById("demoID");
x.style.color = "blue";
  1. 用这个工作代码替换它是否安全:
 demoID.style.color = "blue";

HTML5:

<!DOCTYPE html>
<html>
<body>

<p id="demoID">Click the button to change the color of this paragraph.</p>

<button onclick="myFunction()">Try it</button>

<script>
function myFunction() {
// var x = document.getElementById("demoID");
// x.style.color = "blue";
demoID.style.color = "blue";
}
</script>

</body>
</html>
  1. document.getElementById 相比,性能(速度)如何? ?

编辑:
我做了一个微型基准测试,document.getElementById 快了 3.7 倍:

HTML:

    <input type="checkbox" id="checkboxSigned" onchange="numberBase10changed()">Signed

<div id="div2"></div>

JavaScript:

    let signed=false;
let t0 = performance.now();
for (let i=0; i<1000000; i++){
// signed = document.getElementById("checkboxSigned").checked; // 88ms to 116ms
signed = checkboxSigned.checked; // 369ms to 398ms
g++;
}
div2.innerText = g+"interval = " + Math.trunc( performance.now()-t0 ) + "ms";

signed = document.getElementById("checkboxSigned").checked; 的结果

88ms to 116ms

signed = checkboxSigned.checked; 的结果

369ms to 398ms

预先感谢您的帮助。

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