[英]Which one is correct about calling a function in JavaScript?
我用JavaScript編寫了一個代碼,如下所示:在此代碼中,onClick按鈕要調用函數fadetext()
,而函數fadetext()
本身就是setTimeout。
hex = 255 // Initial color value. function fadetext() { if (hex > 0) { //If color is not black yet hex -= 11; // increase color darkness document.getElementById("sample").style.color = "rgb(" + hex + "," + hex + "," + hex + ")"; setTimeout(fadetext, 20); } else hex = 255 //reset hex value }
<div id="sample" style="width:100%"> <h3>John slowly faded into view</h3> </div> <button onClick=fadetext()>Fade Text</button>
但是,當我參考答案時,以下兩行代碼顯示了差異:
setTimeout("fadetext()",20);
另一個是:
<button onClick="fadetext()">Fade Text</button>
有人可以幫我解釋為什么這也行嗎?
setTimeout
引用對超時到期時應調用的函數的引用,而不是字符串。
盡管setTimeout
可以接受eval
d的字符串, 但不要使用它 , 但與eval()
一樣 , 它也存在安全風險。
setTimeout("fadetext()",20);
應該設置為setTimeout(fadetext,20);
而onclick
屬性全部為小寫。
<button onClick="fadetext()">Fade Text</button>
應為<button onclick="fadetext()">Fade Text</button>
var hex = 255 // Initial color value. function fadetext() { if (hex > 0) { //If color is not black yet hex -= 11; // increase color darkness document.getElementById("sample").style.color = "rgb(" + hex + "," + hex + "," + hex + ")"; setTimeout(fadetext, 20); } else hex = 255 //reset hex value }
<div id="sample" style="width:100%"> <h3>John slowly faded into view</h3> </div> <button onclick="fadetext()">Fade Text</button>
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