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From the following thread (Multiplying an array with a single value by a number?) I got the information that it is not possible to multiply a number to all elements within an array by executing [1, 2]*3. But since I have to do this I was wondering if there is an smart way of doing this?

I know I could write a function which iterates through all elements and multiply a number to each element manually. But I was wondering if there is a smarter way out there?

Maybe there are some libraries out there which implements some math functions where I can multiply a number to all elements of an array?

Or do you think the map function of Array can be used for this purpose?

From the following thread (Multiplying an array with a single value by a number?) I got the information that it is not possible to multiply a number to all elements within an array by executing [1, 2]*3. But since I have to do this I was wondering if there is an smart way of doing this?

I know I could write a function which iterates through all elements and multiply a number to each element manually. But I was wondering if there is a smarter way out there?

Maybe there are some libraries out there which implements some math functions where I can multiply a number to all elements of an array?

Or do you think the map function of Array can be used for this purpose?

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4 Answers 4

Sorted by: Reset to default 5

You can indeed use the map function:

function multiply(input) {
    return input * 3;
}

var myArray = [1, 2];
var myNewArray = myArray.map(multiply);

What this does is perform a function you provide on each element in the array, and return a new array with the results.

If you're already using jQuery, you can make it a little more concise with the each function:

$.each(myArray, function(index, value) {
    myArray[index] = value * 3;
});

This changes the existing array. Although, using the plain-JS approach, you could do myArray = myArray.map(multiply); if you don't want a new variable.

I made a jsFiddle as an example.

This is easy with a library like math.js, which es with matrix support. You could do something like:

var result = math.multiply([1, 2], 3);

or using the expression parser:

var result = math.eval('[1, 2] * 3');

Similar to Jos de Jong's answer, if you are using numericjs you can do

var result = numeric.mul([1, 2], 3);

To give the result [3, 6].

You have not defined your array as an array variable: Just do as following:

function times2(theArray){
 var newArray = [];
 for (i = 0; i < theArray.length; i++) {
  newArray.push(theArray[i] * 2);
 }
 return newArray;
}
document.write("Array double = ",times2([1,2,3,4,5]).toString() , "<br>");

Now it does not matter how many elements you have in your array, it multiplies them by 2. You can choose any number instead of 2.

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