declare.md

Declaring Functions

Functions, like variables, must be declared. Let's declare a function double which accepts an argument called x and returns the double of x :

function double(x) {
    return 2 * x;
}

Functions are also values in JavaScript: they can be stored in variables (just like numbers, strings, etc ...) and given to other functions as arguments :

var double = function(x) {
    return 2 * x;
};

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Declare a function named triple that takes an argument and returns its triple.

var triple = function(x) {
    return x * 3;
}

assert(triple);
assert(triple(4) === 12);
assert(triple(10) === 30);

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