javascript 检查方法对象中是否存在道具。

Posted 2021-05-03

var myObject = {
	a: 2
};

/* in will check the prop's existence in both of object and high level of the [[prototype]] chain object travesal. */
("a" in myObject);	            // true
("b" in myObject);              // false

/* hasOwnProperty will check the prop's existence in the object only. */
myObject.hasOwnProperty( "a" );	// true
myObject.hasOwnProperty( "b" );	// false