Explore how to remove duplicate values from JavaScript arrays and strings
- 2021-01-25 07:08:47
- OfStack
The principle is very clear in the code, so let's go straight to the code example:
var ages = array.map(function(obj) { return obj.age; });
ages = ages.filter(function(v,i) { return ages.indexOf(v) == i; });
console.log(ages); //=> [17, 35]
function isBigEnough(element) {
return element >= 10;
}
var filtered = [12, 5, 8, 130, 44].filter(isBigEnough);
// filtered is [12, 130, 44]
function onlyUnique(value, index, self) {
return self.indexOf(value) === index;
}
// usage example:
var a = ['a', 1, 'a', 2, '1'];
var unique = a.filter( onlyUnique ); // returns ['a', 1, 2, '1']
Better Function(not compatible with IE7)
function unique(array){
return array.filter(function(el, index, arr) {
return index == arr.indexOf(el);
});
}
Function(compatible with IE7)
// Remove duplicate values from the array
function getNoRepeat(s) {
return s.sort().join(",,").replace(/(,|^)([^,]+)(,,\2)+(,|$)/g,"$1$2$4").replace(/,,+/g,",").replace(/,$/,"").split(",");
}
var arr = [" Beijing ", " Shanghai ", " tianjin ", " wuhan ", " Shanghai ", " tianjin ", " wuhan ", " Beijing ", " Shanghai ", " tianjin ", " wuhan ", " tianjin ", " wuhan ", " tianjin ", " wuhan ", " tianjin ", " wuhan ",
" Beijing ", " Shanghai ", " tianjin ", " wuhan ", " Shanghai ", " tianjin ", " wuhan ", " Beijing ", " Shanghai ", " tianjin ", " wuhan ", " tianjin ", " wuhan ", " tianjin ", " wuhan ", " tianjin ", " wuhan ",
" Beijing ", " Shanghai ", " tianjin ", " wuhan ", " Shanghai ", " tianjin ", " wuhan ", " Beijing ", " Shanghai ", " tianjin ", " wuhan ", " tianjin ", " wuhan ", " tianjin ", " wuhan ", " tianjin ", " wuhan "];
arr = getNoRepeat(arr);
alert(arr.length);// 4
alert(arr.toString()); // " Beijing ", " Shanghai ", " tianjin ", " wuhan "
Using map principle
var arr = [" Beijing ", " Shanghai ", " tianjin ", " wuhan ", " Shanghai ", " tianjin ", " wuhan ", " Beijing ", " Shanghai ", " tianjin ", " wuhan ", " tianjin ", " wuhan ", " tianjin ", " wuhan ", " tianjin ", " wuhan ",
" Beijing ", " Shanghai ", " tianjin ", " wuhan ", " Shanghai ", " tianjin ", " wuhan ", " Beijing ", " Shanghai ", " tianjin ", " wuhan ", " tianjin ", " wuhan ", " tianjin ", " wuhan ", " tianjin ", " wuhan ",
" Beijing ", " Shanghai ", " tianjin ", " wuhan ", " Shanghai ", " tianjin ", " wuhan ", " Beijing ", " Shanghai ", " tianjin ", " wuhan ", " tianjin ", " wuhan ", " tianjin ", " wuhan ", " tianjin ", " wuhan "];
var json = {};
for(var i = 0; i < arr.length; i++){
json[arr[i]] = arr[i];
}
arr = new Array();
for(var key in json){
arr.push(key);
}
alert(arr.toString());
// " Beijing ", " Shanghai ", " tianjin ", " wuhan "