46 lines
1.1 KiB
JavaScript
46 lines
1.1 KiB
JavaScript
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// An array with a max length.
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//
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// When max length is surpassed, items are removed from
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// the front of the array.
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// Using Classes to extend Array is unsupported in Babel so this less
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// ideal approach is taken: https://babeljs.io/docs/en/caveats#classes
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export default function RollingArray(maxLength, ...items) {
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const array = new Array(...items);
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array.maxLength = maxLength;
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// Capture the originals of each array method, but
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// associate them with the array to prevent closures.
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array._push = array.push;
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array._splice = array.splice;
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array._unshift = array.unshift;
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array.push = function(...items) {
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const returnValue = this._push(...items);
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const surplus = this.length - this.maxLength;
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if (surplus > 0) {
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this.splice(0, surplus);
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}
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return returnValue;
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};
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array.splice = function(...args) {
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const returnValue = this._splice(...args);
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const surplus = this.length - this.maxLength;
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if (surplus > 0) {
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this._splice(0, surplus);
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}
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return returnValue;
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};
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array.unshift = function() {
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throw new Error('Cannot unshift onto a RollingArray');
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};
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return array;
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}
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