25 lines
854 B
JavaScript
25 lines
854 B
JavaScript
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export default function(arr = [], attribute = 'id') {
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if (!arr.length) {
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return '';
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}
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// this assumes an already sorted array
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// if the array is sorted, we want to compare the first and last
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// item in the array - if they share a prefix, all of the items do
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let firstString = arr[0][attribute];
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let lastString = arr[arr.length - 1][attribute];
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// the longest the shared prefix could be is the length of the match
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let targetLength = firstString.length;
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let prefixLength = 0;
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// walk the two strings, and if they match at the current length,
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// increment the prefixLength and try again
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while (
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prefixLength < targetLength &&
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firstString.charAt(prefixLength) === lastString.charAt(prefixLength)
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) {
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prefixLength++;
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}
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// slice the prefix from the first item
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return firstString.substring(0, prefixLength);
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}
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