Javascriptのvoid操作子
typeof void 0 // "undefined"
console.log(void 0) // undefined
void 0はundefinedのようですが、厳密ではないので、答えられません.void 100、void hello()、void i++という無数の組み合わせの値は何ですか?
The void Operator
The production UnaryExpression : void UnaryExpression is evaluated as follows:
Let expr be the result of evaluating UnaryExpression.
Call GetValue(expr).
Return undefined.
NOTE: GetValue must be called even though its value is not used because it may have observable side-effects.
void ,void undefined.
void , 。
- void
> , (void 0) === undefined, undefined ?
undefined javascript 。 , :
function joke() {
var undefined = "hello world";
console.log(undefined); // "hello world"
}
console.log(undefined); // undefined
, void undefined 。 underscore.js isUndefined :
_.isUndefined = function(obj) {
return obj === void 0;
}
void undefined , ? , 。 AngularJS :
(function(window, document, undefined) {
//.....
})(window, document);
, undefined undefined。
-
> undefined ,void .
`javascript:void(0);` href。 , , , , 。
, URL , , 。 `href="javascript:void(0)` , `void(0)`。
, src image, `src='javascript:void(0)'`, StackOverflow :[What’s the valid way to include an image with no src?](http://stackoverflow.com/questions/5775469/whats-the-valid-way-to-include-an-image-with-no-src)
-
> void , :
`NOTE: GetValue must be called even though its value is not used because it may have observable side-effects.`
? void , 。 , winter :[ js void, undefined, GetValue ?](http://www.zhihu.com/question/22210634)
var happiness = 10;
var girl = {
get whenMarry() {
happiness--;
return 1/0; //Infinity
},
get happiness() {
return happiness;
}
};
console.log(girl.whenMarry); // whenMarry get
console.log(girl.happiness); // 9
void girl.whenMarry; // whenMarry get
console.log(girl.happiness); // 8
delete girl.whenMarry; // whenMarry get
console.log(girl.happiness); // 8
, (whenMarry),happiness 1。 , girl.whenMarry, void girl.whenMarry happiness--。 void delete delete girl.whenMarry, happiness , delete girl.whenMarry 。
-
> void :
void 0 undefined undefined , void 0 。
\のhrefはクリック にページジャンプが しないことを します。 されたsrcは、サーバーにごみの がないことを する。
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