| 1 | /**
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| 2 | * @name arrayFlatten
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| 3 | * @summary Merge T[][] into T[]
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| 4 | * @description
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| 5 | * Returns a new array with all arrays merged into one
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| 6 | * @example
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| 7 | * <BR>
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| 8 | *
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| 9 | * ```javascript
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| 10 | * import { arrayFlatten } from '@polkadot/util';
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| 11 | *
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| 12 | * arrayFlatten([[1, 2], [3, 4], [5]]); // [1, 2, 3, 4, 5]
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| 13 | * ```
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| 14 | */
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| 15 | export function arrayFlatten(arrays) {
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| 16 | const num = arrays.length;
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| 17 | // shortcuts for the empty & single-entry case
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| 18 | if (num === 0) {
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| 19 | return [];
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| 20 | }
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| 21 | else if (num === 1) {
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| 22 | return arrays[0];
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| 23 | }
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| 24 | // pre-allocate based on the combined size
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| 25 | let size = 0;
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| 26 | for (let i = 0; i < num; i++) {
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| 27 | size += arrays[i].length;
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| 28 | }
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| 29 | const output = new Array(size);
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| 30 | let i = -1;
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| 31 | for (let j = 0; j < num; j++) {
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| 32 | const a = arrays[j];
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| 33 | // instead of pushing, we just set the entries
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| 34 | for (let e = 0, count = a.length; e < count; e++) {
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| 35 | output[++i] = a[e];
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| 36 | }
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| 37 | }
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| 38 | return output;
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| 39 | }
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