.push() value to JavaScript array (n) times using .fill()? - Stack Overflow

Is it possible to .push() a value to an array but replicate the pushed value n times without using a traditional loop to perform the replication? For instance using .fill(). The examples I have seen declare a new Array() with a length of n, and .fill() it with a value. However, I have not seen any examples dealing with .push(), so I'm not even sure it is possible.

Example of what I'm looking for:

var my_array = [];
for (var i = 0; i < 5; i++) {
    my_array.push(5);
};

Scenario:

I'm pulling values from three different arrays or objects to populate a single matrix that will be ran through a Munkres (Hungarian) algorithm, in order to avoid introducing another loop I would like to .push values to the matrix and use .fill() to repeat the value n times.

Example:

var s = […];
var a = […];
var p = […];

var matrix = [];
for (var i = 0; i < s.length; i++) {
    var preferences = [];
    for (var j = 0; j < p.length; j++ {
        var pid = p[j];
        for (var k = 0; k < a.length; k++ {
            if (pid == a[k]) {
                for (var l = 0; l < 5; l++) {  // <-- THIS.
                    preferences.push(a[k]);
                };
            };
        };
    };
    matrix.push(preferences);
};

Is it possible to .push() a value to an array but replicate the pushed value n times without using a traditional loop to perform the replication? For instance using .fill(). The examples I have seen declare a new Array() with a length of n, and .fill() it with a value. However, I have not seen any examples dealing with .push(), so I'm not even sure it is possible.

Example of what I'm looking for:

var my_array = [];
for (var i = 0; i < 5; i++) {
    my_array.push(5);
};

Scenario:

I'm pulling values from three different arrays or objects to populate a single matrix that will be ran through a Munkres (Hungarian) algorithm, in order to avoid introducing another loop I would like to .push values to the matrix and use .fill() to repeat the value n times.

Example:

var s = […];
var a = […];
var p = […];

var matrix = [];
for (var i = 0; i < s.length; i++) {
    var preferences = [];
    for (var j = 0; j < p.length; j++ {
        var pid = p[j];
        for (var k = 0; k < a.length; k++ {
            if (pid == a[k]) {
                for (var l = 0; l < 5; l++) {  // <-- THIS.
                    preferences.push(a[k]);
                };
            };
        };
    };
    matrix.push(preferences);
};

• javascript
• arrays

Share Follow edited Mar 25, 2019 at 23:08 artomason asked Mar 25, 2019 at 23:04 artomasonartomason 4,03366 gold badges2828 silver badges4545 bronze badges 2

• I think you need to use fill, but without push - push returns the new length of the array. – Jack Bashford Commented Mar 25, 2019 at 23:08
• The problem is I need to append the values to the preferences array so they are retained each iteration. I think if I create an array with the desired values and .push() that to the preferences array it would result in [[ ],[ ],[ ]] – artomason Commented Mar 25, 2019 at 23:09

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1 Answer 1

Sorted by: Reset to default 8

You could use concat and fill:

preferences = preferences.concat(Array(5).fill(a[k]));