JavaScript logical operator

Question

Below is my JavaScript code:

THREEx.KeyboardState.prototype.pressed  = function(keyDesc)

{

    var keys    = keyDesc.split("+");

    for(var i = 0; i < keys.length; i++){

        var key     = keys[i];

        var pressed;

        if( THREEx.KeyboardState.MODIFIERS.indexOf( key ) !== -1 ){

            pressed = this.modifiers[key];

        }else if( Object.keys(THREEx.KeyboardState.ALIAS).indexOf( key ) != -1 ){

            pressed = this.keyCodes[ THREEx.KeyboardState.ALIAS[key] ];

        }else {

            pressed = this.keyCodes[key.toUpperCase().charCodeAt(0)];

        }

        if( !pressed)   return false;

    };

    return true;

}

Here’s the line I have the problem with:

 if( THREEx.KeyboardState.MODIFIERS.indexOf( key ) !== -1 )

Can anyone tell me what’s the meaning of != ?

Answer 1

When you compare 0 ==0, it returns true. For 0 == “0” it returns false. Similarly, 0! == “0” returns true, while 0! == 0 returns false. 

It means two values are compared not only by their implied value but also by their type. 

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