10 examples of 'how to find duplicate values in array using javascript' in JavaScript

270
export function getDuplicateNames(indexableArray: { name: string }[]): string[] {
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  const seen: { [name: string]: number } = {};
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  const duplicates: string[] = [];
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  indexableArray.forEach((element: { name: string }) => {
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    const { name } = element;
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    const count = seen[name] || 0;
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    if (count === 1) {
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      duplicates.push(name);
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    }
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    seen[name] = count + 1;
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  });
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  return duplicates;
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}

52
function horribleDuplicates (array) {
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    for (var i = 0; i < array.length; i++) {
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        for (var j = 0; j < array.length; j++) {
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            if (array[i] == array[j]) {
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                return true
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            }
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        }
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    }
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    return false
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}

30
function duplicateArray(arr) {
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  var newArr = [];
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  for(var i=0, arrSize=arr.length; i<arrSize; i++) {
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    newArr.push(arr[i]);
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  }
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  return newArr;
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}

64
function duplicateArray(array) {
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  return array.clone ? array.clone() : new Array(array.length);
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}

53
function testForDuplicates(obj, key, dups) {
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    test(wrap(key) + ' has no duplicate', function() {
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        var id = key.toUpperCase(),
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            exists = id in dups;
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        if (exists) {
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            dups[id].push(key);
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        } else {
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            dups[id] = [ key ];
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        }
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        assert.ok(!exists, dups[id].join(', '));
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    });
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}

25
function removeDuplicates_for_loop(arr) {
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  let res = [];
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  const len = arr.length;
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  for (let i = 0; i < len; i++) {
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    if (res.indexOf(arr[i]) === -1) {
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      res.push(arr[i]);
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    }
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  }
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  return res;
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}

79
export function uniqueValues<T>(array: T[]): T[] {
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  return Array.from(new Set(array));
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}

12
function uniqueAdd(obj, key, values) {
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  const a = (obj[key] = obj[key] || []);
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  for (let i = 0; i < values.length; i++) {
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    if (a.indexOf(values[i]) === -1) {
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      a.push(values[i]);
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    }
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  }
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}

48
function removeDuplicates(_array) {
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	var _uniques = [], _dupl = [], i = 0;
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	for (i; i <= _array.length; i++) {
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		var v = _array[i];
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		console.log(i + '-' + v);
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		if (_array.lastIndexOf(v) > i || _dupl.indexOf(v) > -1) {
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			_dupl.push(v);
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		} else {
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			_uniques[_uniques.length] = v;
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		}
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	}
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	return $.grep(_uniques, function(n, i) {
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		return (n);
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	});
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}

18
function unique<T>(array: T[]): T[] {
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  const map: {
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    [key: string]: T;
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  } = {};
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  array.forEach(i => {
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    const key = String(i);
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    if (map[key]) return;
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    map[key] = i;
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  });
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  return Object.keys(map).map(key => map[key]);
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}