CODEWITHSUNDEEP
javascriptvariablesoperators
user5154997
user5154997

Reputation:

The negation operator in Javascript ? how is it working?

I have code is below : 

var x = 4 
var y = --x;

Why when I running the result is : 

console.log("value of x: ",x); //outputs 3 
console.log("value of y: ",y); //outputs 3

Why not is : 

console.log("value of x: ",x); //outputs 4 
console.log("value of y: ",y); //outputs 3

Upvotes: 0

Views: 80

Answers (2)

bhansa
bhansa

Reputation: 7504

Here in var y = --x; --x will set x to x-1 and returns the updated value.

If x is 3, then --x sets x to 2 and returns 2, whereas x-- returns 3 and, only then, sets x to 2.

Have a look at Arithmetic operators

Upvotes: 0

Nicholas Tower
Nicholas Tower

Reputation: 84912

the decrement operator can be used both as a prefix, and as a suffix, and it has different behavior. In prefix position it means "decrement first, and then return the value" in postfix position it means "return the value first, and then decrement".

So var y = --x means "change x to equal itself -1, then assign the resulting value to y"

var y = x-- means "assign the value of x to y, then change x to equal itself -1"

If you just want to do a calculation and not change what x equals, then do var y = x - 1

Upvotes: 1

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