So let’s do this one first

If (a==1&&a==2&&a=3){console.log(' printout succeeded '); }Copy the code

Method 1: Use the toString method.

=== === === === === === === ===

1. When an object == string, the object.toString() method converts the object to a string and compares 2. Null ==undefined, but not with other values. The rest is going to be converted to numbersCopy the code

So we can rewrite the toString method:

var a={ i=0; toString:(){ return ++this.i; }} if(a==1&&a==2&&a=3){console.log(' printable successfully '); }Copy the code

The toString method is called on each comparison, incrementing the value by 1, and then all are exactly equal.

Another way is to use the shift of the array

Var a = [1, 2, 3]; a.toString=a.shift(); If (a==1&&a==2&&a=3){console.log(' printable successfully '); }Copy the code

Method two, using data hijacking

For Object.defineProperty(), there are get() and set() methods. After listening for a value, get() is called each time the value is fetched and set() is called each time the value is set. Obj.defineproperty () can be used because each time a==1 we need to get the value of a first and then determine whether it is equal.

var i=0; var a; Object.defineProperty(window,'a',{ get(){ return ++i; }}) if(a==1&&a==2&&a=3){console.log(' printable successfully '); }Copy the code