EN
TypeScript - foreach array of arrays
3 points
In this article, we would like to show you how to use a nested for-each loop to iterate an array of arrays in TypeScript.
This section shows how to use forEach method to iterate over an array of arrays.
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const array: string[][] = [2
['item 1', 'item 2'],3
['item 3', 'item 4'],4
];5
6
array.forEach((items: string[], index1: number): void => {7
items.forEach((item: string, index2: number): void => {8
console.log(item);9
});10
});Output:
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item 12
item 23
item 34
item 4Note:
Array.prototype.forEachmethod was introduced in ES5 (ECMAScript 2009).
This section shows how to use for-of loop construction to iterate over an array of arrays.
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const array: string[][] = [2
['item 1', 'item 2'],3
['item 3', 'item 4'],4
];5
6
for (const items of array) {7
for (const item of items) {8
console.log(item);9
}10
}Output:
xxxxxxxxxx1
item 12
item 23
item 34
item 4Note:
for-ofloop was introduced in ES6 (ECMAScript 2015).
This section shows how to use for-in loop construction to iterate over an array of arrays.
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const array: string[][] = [2
['item 1', 'item 2'],3
['item 3', 'item 4'],4
];5
6
for (const key1 in array) {7
if (array.hasOwnProperty(key1)) {8
const items = array[key1];9
for (const key2 in items) {10
if (items.hasOwnProperty(key2)) {11
console.log(items[key2]);12
}13
}14
}15
}Output:
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item 12
item 23
item 34
item 4Note: using
for-inloop with array is risky because of possible additional array properties -array.hasOwnProperty(key)method solves the problem.
