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Array Methods

Array prototype methods available in SSJS — which work natively, which need polyfills, and safe ES3/ES5 alternatives for missing methods.

Modifying Arrays

push / pop

var arr = [1, 2, 3];
arr.push(4);       // [1, 2, 3, 4]
var last = arr.pop(); // 4, arr = [1, 2, 3]

shift / unshift

var arr = [1, 2, 3];
var first = arr.shift();   // 1, arr = [2, 3]
arr.unshift(0);            // arr = [0, 2, 3]

splice

Array.prototype.splice is broken in SFMC SSJS. The method exists but ignores its first two parameters. Always apply the polyfill from Polyfills before using it.

// After applying the polyfill:
var arr = ["a", "b", "c", "d"];
// Remove 1 element at index 1
arr.splice(1, 1);           // ["a", "c", "d"]

// Replace element
arr.splice(1, 1, "X");      // ["a", "X", "d"]

// Insert without removing
arr.splice(1, 0, "B");      // ["a", "B", "X", "d"]

reverse / sort

var arr = [3, 1, 4, 1, 5, 9];
arr.sort(function(a, b) { return a - b; });  // ascending
arr.reverse();  // descending

Reading Arrays

slice

var arr = [0, 1, 2, 3, 4];
arr.slice(1, 3);  // [1, 2]
arr.slice(-2);    // [3, 4]
arr.slice();      // copy of arr

join

var parts = ["Hello", "World"];
parts.join(", ");   // "Hello, World"
parts.join("");     // "HelloWorld"
parts.join(" / ");  // "Hello / World"

indexOf (polyfill required)

Polyfillable Methods

The following methods require polyfills from Polyfills. Once applied they work correctly.

Method Notes
Array.prototype.copyWithin(targetIndex, startIndex, count) ⚠️ Unavailable
Array.prototype.entries() ⚠️ Unavailable
Array.prototype.fill(value[, start[, end]]) ⚠️ Unavailable
Array.prototype.findIndex(fn) ⚠️ Unavailable
Array.prototype.includes(searchValue) ⚠️ Unavailable
Array.prototype.indexOf(searchValue[, fromIndex]) ⚠️ Unavailable
Array.prototype.lastIndexOf(searchValue[, fromIndex]) ⚠️ Broken — always returns -1
Array.prototype.splice(start[, deleteCount[, ...]]) ⚠️ Broken — ignores parameters
Array.isArray(value) ⚠️ Unavailable
Array.of(...) ⚠️ Unavailable

Iteration (Use for loops)

In SSJS, forEach, map, filter, reduce, some, and every are not available. Use for loops instead.

forEach equivalent

// Instead of:  arr.forEach(function(item) { ... })
for (var i = 0; i < arr.length; i++) {
    var item = arr[i];
    // process item
}

map equivalent

// Instead of: var doubled = arr.map(function(x) { return x * 2; })
var doubled = [];
for (var i = 0; i < arr.length; i++) {
    doubled.push(arr[i] * 2);
}

filter equivalent

// Instead of: var evens = arr.filter(function(x) { return x % 2 === 0; })
var evens = [];
for (var i = 0; i < arr.length; i++) {
    if (arr[i] % 2 === 0) {
        evens.push(arr[i]);
    }
}

reduce equivalent

// Instead of: var sum = arr.reduce(function(acc, x) { return acc + x; }, 0)
var sum = 0;
for (var i = 0; i < arr.length; i++) {
    sum += arr[i];
}

find equivalent

// Instead of: var found = arr.find(function(x) { return x.id === targetId; })
var found = null;
for (var i = 0; i < arr.length; i++) {
    if (arr[i].id === targetId) {
        found = arr[i];
        break;
    }
}

some/every equivalent

// Instead of: arr.some(function(x) { return x > 10; })
var hasLarge = false;
for (var i = 0; i < arr.length; i++) {
    if (arr[i] > 10) { hasLarge = true; break; }
}

// Instead of: arr.every(function(x) { return x > 0; })
var allPositive = true;
for (var i = 0; i < arr.length; i++) {
    if (arr[i] <= 0) { allPositive = false; break; }
}

reduceRight equivalent

// Instead of: arr.reduceRight(function(acc, x) { return acc + x; }, 0)
var sum = 0;
for (var i = arr.length - 1; i >= 0; i--) {
    sum += arr[i];
}

Array.isArray

Flattening / Concatenation

Array.prototype.flat() and Array.prototype.flatMap() are ES6+ and not available. Use:

// Concat arrays
var combined = arr1.concat(arr2);

// Manual flatten (one level)
function flatten(arr) {
    var result = [];
    for (var i = 0; i < arr.length; i++) {
        if (typeof arr[i] === "object" && arr[i].length !== undefined) {
            for (var j = 0; j < arr[i].length; j++) {
                result.push(arr[i][j]);
            }
        } else {
            result.push(arr[i]);
        }
    }
    return result;
}

See Also

See Also