通过对象键将数组项移到前面

Question

所以我有一个对象数组;

[
    {
        "foo": 2,
        "bar": "test"
    },
    {
        "foo": 19,
        "bar": "value"
    },
    {
        "foo": 7,
        "bar": "temp"
    }
]

我需要将具有特定值的对象移动foo到数组的开头.值始终在对象中,但不保证对象将在数组中.

所以在运行之后moveToFront(19);,我有以下内容:

[
    {
        "foo": 19,
        "bar": "value"
    },
    {
        "foo": 2,
        "bar": "test"
    },
    {
        "foo": 7,
        "bar": "temp"
    }
]

我该怎么做呢？

Answer 1

这应该是相当简单的,你搜索你的数组,直到你找到你正在寻找的项目,然后你splice出来,unshift它回到开头.像这样的东西:

// foo is the target value of foo you are looking for
// arr is your array of items
// NOTE: this is mutating. Your array will be changed (unless the item isn't found)
function promote(foo, arr) {
    for (var i=0; i < arr.length; i++) {
        if (arr[i].foo === foo) {
            var a = arr.splice(i,1);   // removes the item
            arr.unshift(a[0]);         // adds it back to the beginning
            break;
        }
    }
    // Matching item wasn't found. Array is unchanged, but you could do something
    // else here if you wish (like an error message).
}

如果没有匹配foo值的项,那么这对您的数组不起作用.如果需要,您可以使用错误消息处理它.

Answer 2

最短路:Array.some

var data = [{"foo":2}, {"foo":19}, {"foo":7}, {"foo":22}]

// move {foo:7} to the front
data.some(item => item.foo == 7 && data.unshift(item))


// print result
console.log(data)

findIndex方法会很有帮助

var data = [{"foo":2}, {"foo":19}, {"foo":7}, {"foo":22}]

// move {foo:7} to the front
const clonedData = [...data]
clonedData.some((item, i, arr) => item.foo == 7 && arr.unshift(item))

// print result
console.log(clonedData)

var data = [{"foo":2}, {"foo":19}, {"foo":7}, {"foo":22}]

// find the index of the target array item:
var itemIndex = data.findIndex(item => item.foo == 7); 

data.splice(
    0,                           // new index,
    0,                           // no removal
    data.splice(itemIndex, 1)[0] // detach the item and return it
);

// print result
console.log(data)

如果您使用lodash并且需要支持旧版浏览器,请使用以下some()方法:

findIndex()

这将使用键将Array Object移动到数组_.findIndex的开头.