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sebringj/findRepeatedIndex.js

Last active April 9, 2021 18:32
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finds first repeated value and returns index
Raw
findRepeatedIndex.js
const findRepeatedIndex = arr => [...arr].findIndex(function(item) {
this.lookup = this.lookup || {};
return this.lookup[item] && 1 || (this.lookup[item] = 1) && 0;
});
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