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var arr = ['test0','test2','test0'];
Like the above,there are two identical entries with value "test0",how to check it most efficiently?
963
Using the indexOf() method In this method, what we do is that we compare the index of all the items of an array with the index of the first time that number occurs. If they don't match, that implies that the element is a duplicate. All such elements are returned in a separate array using the filter() method.
function checkIfArrayIsUnique(myArray) { for (var i = 0; i < myArray. length; i++) { for (var j = i+1; j < myArray. length; j++) { if (myArray[i] == myArray[j]) { return true; // means there are duplicate values } } } return false; // means there are no duplicate values. }
Simple Approach: The idea is to use nested loop and for each element check if the element is present in the array more than once or not. If present, then store it in a Hash-map.
If you sort the array, the duplicates are next to each other so that they are easy to find:
arr.sort();
var last = arr[0];
for (var i=1; i<arr.length; i++) {
if (arr[i] == last) alert('Duplicate : '+last);
last = arr[i];
}
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