Combine 2 arrays into a multidimensional array?

Question

This is based on my last question.

I have these arrays:

var array1 = new Array ("Pepsi", "Coke", "Juice", "Water");
var array2 = new Array ("35",    "17",   "21",    "99");

And I want to combine them to form a multidimensional array like this:

[
    ["Pepsi","35"]
    ["Coke", "17"]
    ["Juice","21"]
    ["Water","99"]
]

I tried this script:

Values=[];

for (i = 0; i < array1.length; i++) {
    Values[i] = Array(array1[i], array2[i]);
}

But it gave a result like this (correct values, incorrect names):

[
    ["a","35"]
    ["c","17"]
    ["E","21"]
    ["I","99"]
]

Where would the capital E and I come from, or are those typos? — Yatrix
– Yatrix, Commented May 16, 2012 at 17:41

Sampson · Accepted Answer · 2012-05-16 17:54:47Z

18

var array1 = ["Pepsi", "Coke", "Juice", "Water"],
    array2 = ["35", "17", "21", "99"],
    result = [], i = -1;

while ( array1[++i] ) { 
  result.push( [ array1[i], array2[i] ] );
}

As written, this solution assumes you will only ever be using strings. As @ajax333221 has pointed out in the comments below, this would cause problems if you were to involve boolean or int values into this solution. As such, I'd like to propose an improvement that will accomplish your goals, while not tripping over difficult values and types:

var array1 = [false, 0, "Juice", -1],
    array2 = ["35", "17", "21", "99"],
    result = [];

for ( var i = 0; i < array1.length; i++ ) {
  result.push( [ array1[i], array2[i] ] );
}

edited May 16, 2012 at 17:54

answered May 16, 2012 at 17:34

Sampson

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4 Comments

ajax333221 Over a year ago

you assumed he will always work with strings. If he works with other things like numbers 0 or booleans false, there will be problems

Sampson Over a year ago

@ajax333221 Yes, I'm assuming the question represents the problem.

ajax333221 Over a year ago

@JonathanSampson And I will now assume you don't like to write maintainable and flexible code

Sampson Over a year ago

@ajax333221 I appreciate your advice, and I've added a for loop to side-step any issues with types and values of the falsey nature.

cliffs of insanity · Accepted Answer · 2012-05-16 17:59:12Z

13

You can use .map() on Arrays.

var Values = array1.map(function(v,i) {
    return [v, array2[i]];
});

See the MDN shim for older browsers.

live demo: http://jsfiddle.net/D9rjf/

If you're going to do this operation quite a bit, you could make a reusable function.

In this example, I extended Array.prototype, but that's not necessary if you don't like that.

Array.prototype.combine = function(arr) {
    return this.map(function(v,i) {
        return [v, arr[i]];
    });
};

var Values = array1.combine(array2);

live demo: http://jsfiddle.net/D9rjf/1/

edited May 16, 2012 at 17:59

answered May 16, 2012 at 17:43

cliffs of insanity

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1 Comment

Larry Over a year ago

not enough answers on SO like this using non-destructive methods to create arrays

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