Does valueOf always override toString in javascript?

Question

Is there any expression where by an object\'s toString method is implicitly called overriding its valueOf method?

In the examples below, valueOf is alw

Answer 1

The + operator on Date objects uses toString not valueOf. Also if valueOf returns a non-primitive value then the toString method is called next. (JavaScript - The definitive guide, section 3.14) Using your example:

var result = "4" + {
    toString: function () {
        return "4";
    },
    valueOf: function () {
        return this; // returning an object, not a primitive
    }
};

Result is now 44.