Javascript Array.push() 和唯一项

Array.push() and unique items

提问by Tomek Buszewski

I have a simple case of pushing unique values into array. It looks like this:

我有一个将唯一值推入数组的简单案例。它看起来像这样：

  this.items = [];

  add(item) {
    if(this.items.indexOf(item) > -1) {
      this.items.push(item);
      console.log(this.items);
    }
  }

Seems pretty straight-forward, right? No, as it appears. It doesn't add any values. I am sure it's some kind of silly mistake on my side, but I can't seem to find it.

看起来很直接，对吧？不，正如它所显示的那样。它不会添加任何值。我确定这是我这边的某种愚蠢的错误，但我似乎无法找到它。

回答by JagsSparrow

Yep, it's a small mistake.

是的，这是一个小错误。

if(this.items.indexOf(item) === -1) {
    this.items.push(item);
    console.log(this.items);
}

回答by Sergey Zhigalov

You can use Setstructure from ES6 to make your code faster and more readable:

您可以使用ES6 中的Set结构使您的代码更快、更易读：

// Create Set
this.items = new Set();

add(item) {
    this.items.add(item);

    // Set to array
    console.log([...this.items]);
}

回答by lachlan.p.jordan

try .includes()

尝试.includes()

[1, 2, 3].includes(2);     // true
[1, 2, 3].includes(4);     // false
[1, 2, 3].includes(3, 3);  // false
[1, 2, 3].includes(3, -1); // true
[1, 2, NaN].includes(NaN); // true

so something like

所以像

const array = [1, 3];
if (!array.includes(2))
    array.push(2);

note the browser compatibility at the bottom of the page, however.

但是，请注意页面底部的浏览器兼容性。

回答by Vivek Kumar

I guess ES6 has set data structure, which you can use for unique entries

我猜 ES6 已经设置了数据结构，您可以将其用于唯一条目

回答by KitKit

If you use Lodash, take a look at _.unionfunction:

如果您使用Lodash，请查看_.union功能：

let items = [];
items = _.union([item], items)

回答by ManoDestra

Your logic is saying, "if this item exists already, then add it." It should be the opposite of that.

你的逻辑是，“如果这个项目已经存在，那就添加它。” 应该是相反的。

Change it to...

将其更改为...

if (this.items.indexOf(item) == -1) {
    this.items.push(item);
}

回答by fdfey

You have to use === -1, if it equals to -1 i.e. item is not available in your array:

您必须使用 === -1，如果它等于 -1，即项目在您的数组中不可用：

  this.items = [];

  add(item) {
    if(this.items.indexOf(item) === -1) {
      this.items.push(item);
      console.log(this.items);
    }
  }

回答by Martin Morawiec

var helper = {};
for(var i = 0; i < data.length; i++){
  helper[data[i]] = 1; // Fill object
}
var result = Object.keys(helper); // Unique items

回答by Rohit Agrohia

Push always unique value in array

在数组中始终推送唯一值

ab = [
     {"id":"1","val":"value1"},
     {"id":"2","val":"value2"},
     {"id":"3","val":"value3"}
   ];



var clickId = [];
var list = JSON.parse(ab);
$.each(list, function(index, value){
    if(clickId.indexOf(value.id) < 0){
        clickId.push(value.id);
    }
});

回答by Trilok Singh

Using Set

使用集合

this.items = new Set();
this.items.add(1);
this.items.add(2);
this.items.add(1);
this.items.add(2);

console.log(Array.from(this.items)); // [1, 2]