ES5方法

双层循环

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function uniq(array){
  var result=[];
  for(var i=0;i<array.length;i++){
    for(var j=0;j<result.length;j++){
      if(array[i] === result[j]){
        break;
      }
    }
    // 如果array[i]是唯一的，那么执行完循环，j等于result.length
    if (j === result.length) {
        result.push(array[i])
    }
  }
  return result;
}

var arr = [1,2,2,4,9,6,7,5,2,3,5,6,5];
console.log(uniq(arr));

indexOf

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function uniq(array){
    var temp = []; //一个新的临时数组
    for(var i = 0; i < array.length; i++){
        if(temp.indexOf(array[i]) == -1){
            temp.push(array[i]);
        }
    }
    return temp;
}

var arr = [1,2,2,4,9,6,7,5,2,3,5,6,5];
console.log(uniq(arr));

hashtable利用对象的属性唯一

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function uniq(array){
  var result=[],
      hash={};
  array.forEach(function(item){
    if(!hash[item]){
      result.push(item);
      hash[item] = true;
    }
  });
  return result;
}

var arr = [1,2,2,4,9,6,7,5,2,3,5,6,5];
console.log(uniq(arr));

复杂数据结构处理

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function uniq(array){
  var unique={};
  array.forEach(function(item){
    unique[JSON.stringify(item)] = item;
  });

  array = Object.keys(unique).map(function(data){
    return JSON.parse(data)
  });
  return array;
}
var arr = [
  {name: 'lee', from:'beijing'},
  {name: 'jersey', from: 'shanghai'},
  {name: 'tom',from:'beijing'},
  {name: 'jersey', from: 'shanghai'}
]
console.log(uniq(arr))

ES6方法

ES6 Set去重

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function uniq (array) {
  return Array.from(new Set(array))
}
var arr = [1,2,2,4,9,6,7,5,2,3,5,6,5];
console.log(uniq(arr))

ES6 […new Set(arr)]

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[...new Set(arr)]
var arr = [1,2,2,4,9,6,7,5,2,3,5,6,5];
console.log([...new Set(arr)])

filter

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var arr = [1,2,2,4,9,6,7,5,2,3,5,6,5];
arr.filter((item, index) => arr.indexOf(item) === index);

reduce

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var arr = [1,2,2,4,9,6,7,5,2,3,5,6,5];
arr.reduce((unique, item) => 
  unique.includes(item) ? unique : [...unique, item], []);