Some minor issues about type conversion in js

This time I will bring you some minor questions about type conversion in js. What are the precautions about type conversion in js? The following are Let’s take a look at practical cases.

var str = false + 1;
var demo = false == 1;
if(typeof(a)&&-true + (+undefined) + ''){  console.log("我能输出吗？");
}
if(11 + '11' * 2 == 33) {  console.log("我能输出吗？");
}
!!' ' + !!'' - !!false||document.console.log("我能输出吗？");;

The following is the answer analysis

var str = false + 1;       //1
var demo = false == 1;       //false 
if(typeof(a)&&-true + (+undefined) + ''){  console.log("我能输出吗？");
}//输出  我能输出吗？//typeof(a) ==> typeof(undefined)  ==> "undefined"//"undefined"&&-true ==> -true ==> -1//+undefined ==> NaN//+"",结果是 "NaN"//转换成Boolean值为true
if(11 + '11' * 2 == 33) {  console.log("我能输出吗？");
}//11 + '11' * 2 == 33  ==>  11 + 22 == 33 ==>   11 + false ==> 11//输出  我能输出吗？
!!' ' + !!'' - !!false || document.console.log("我能输出吗？");
//没有输出  我能输出吗？
//!!把后面的变成Boolean值，!!' ' + !!''  ==>  true + false //true + false + false  ==> 1
//||符号前面为true就不往后走了

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to the php Chinese websiteOther related articles!

Recommended reading:

Nodejs uses Mongoose to create models and APIs

JavaScript's var and this, { }With function

Nodejs form verification and image upload

The above is the detailed content of Some minor issues about type conversion in js. For more information, please follow other related articles on the PHP Chinese website!