Javascript - Operator Subtract Operator

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Introduction

The subtract operator - is used as math operator: 

var result = 2 - 1;

The subtract operator has rules to deal with the variety of type:

Operand
 Result
If the two operands are numbers
 perform arithmetic subtract and return the result.
If either operand is NaN
 the result is NaN.
If Infinity is subtracted from Infinity
 the result is NaN.
If -Infinity is subtracted from -Infinity
 the result is NaN.
If -Infinity is subtracted from Infinity
 the result is Infinity.
If Infinity is subtracted from -Infinity
 the result is -Infinity.
If +0 is subtracted from +0
 the result is +0.
If -0 is subtracted from +0
 the result is -0.
If -0 is subtracted from -0
 the result is +0.
If either operand is a string, a Boolean, null, or undefined

 it is converted to a number using Number() and the arithmetic is calculated using the previous rules.
If that conversion results in NaN, then the result of the subtraction is NaN.
If either operand is an object,


 its valueOf() method is called to retrieve a numeric value to represent it.
If that value is NaN, then the result of the subtraction is NaN.
If the object doesn't have valueOf() defined, then toString() is called and the resulting string is converted into a number.

Demo

var result1 = 5 - true;    //4 because true is converted to 1
console.log(result1);/* w w w  .  jav  a2s.c o m*/
var result2 = NaN - 1;     //NaN 
console.log(result2);
var result3 = 5 - 3;       //2 
console.log(result3);
var result4 = 5 - "";      //5 because "" is converted to 0 
console.log(result4);
var result5 = 5 - "2";     //3 because "2" is converted to 2 
console.log(result5);
var result6 = 5 - null;    //5 because null is converted to 0 
console.log(result6);

Result

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