Implicit type conversion in JS

This time I will bring you the implicit type conversion in JS, what are the precautions when using the implicit type conversion in JS, the following is a practical case, let’s take a look take a look.

isNaN()

To determine whether it is NaN, Number() will be called first, and then compared with NaN after conversion

isNaN(123);         //falseisNaN("123");       //false，字符串//Number('123')  ==> isNaN(123)  ==> falseisNaN("null");      //true，字符串//Number("null")  ==> isNaN(NaN)  ==> trueisNaN(null);        //false，null对象//Number(null)  ==> isNaN(0)  ==> falseisNaN(undefined);   //true//Number(undefined)  ==> isNaN(NaN)  ==> trueisNaN("123bcd");    //true//Number("123bcd")  ==> isNaN(NaN)  ==> true

++/-- +/- (Auto-increment and self-decrement sign, one-yuan positive and negative)

var a = '123'; a ++;     //a 124var b = 'abc'; a ++;     //b NaN; typeof(b) ==> numbervar c = + 'abc';         //c NaN; typeof(c) ==> number

+ plus sign, when there is a string on both sides of the plus sign, String() will be called to combine both Become a string

var a = 1 + "123";      //"1123"var b = "abc" + 12;     //"abc12"

-*% (addition, subtraction, multiplication and division), Number() will be called, and both sides will be converted into numeric types

var a = 1/"2";      //a  0.5;typeof(a)  number

&& || ! Convert to boolean value

> <  >= <= == 有字符串和数字比较的，隐式的调用Number()转换成数字
//undefined ,null,"abc"都转换成NaNundefined > 0       //falseundefined < 0       //falseundefined == 0      //falsenull > 0            //falsenull < 0            //falsenull == 0           //false"abc" > 0           //false"abc" < 0           //false"abc" == 0          //false

== !=

undefined == undefined //truenull == null           //trueNaN == NaN             //false

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

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