Javascript 三 (3) 个等号
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Triple (3) Equal Signs
提问by FastTrack
Possible Duplicate:
JavaScript === vs == : Does it matter which “equal” operator I use?
I asked another questionhere and received a great answer as follows:
我在这里问了另一个问题，得到了一个很好的答案，如下所示：
$(document).on("keydown", function (e) {
if (e.which === 8 && !$(e.target).is("input, textarea") || $(e.target).is('[readonly]')) {
e.preventDefault();
}
});
Notice the three equal signs ===in the if-statement. I have always thought you only needed two equal signs ==for a javascript/jQuery if-statement. Is there any reason for the three?
注意===if 语句中的三个等号。我一直认为==javascript/jQuery if 语句只需要两个等号。这三个有什么原因吗？
UPDATE
更新
Sorry for the duplicate question - I searched but didn't find any good questions. I guess I was using the wrong search terms.
很抱歉重复的问题 - 我搜索过但没有找到任何好的问题。我想我使用了错误的搜索词。
回答by Jeshurun
Triple equal sign in javascript means equality without type coercion.
javascript 中的三个等号表示没有类型强制的相等。
For example:
例如：
1=="1" // true, automatic type coersion
1==="1" // false, not the same type.
回答by Justin
Three equal signs indicates both the value and type are equal.
三个等号表示值和类型都相等。
