所以我有一个对象数组；
[
{
"foo": 2,
"bar": "test"
},
{
"foo": 19,
"bar": "value"
},
{
"foo": 7,
"bar": "temp"
}
]
我需要将一个具有特定值 foo 的对象移动到数组的开头。该值始终在对象中，但不能保证该对象在数组中。
因此，在运行 moveToFront(19); 之后，我会得到以下结果：
[
{
"foo": 19,
"bar": "value"
},
{
"foo": 2,
"bar": "test"
},
{
"foo": 7,
"bar": "temp"
}
]
我该如何着手做这件事？
这应该是相当简单的，你搜索数组直到找到你要查找的项，然后将其splice出来，并将其unshift回到开头。像这样：
// 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).
}
foo值相对应的项，则这不会对您的数组产生任何影响。如果需要，您可以通过错误消息来处理此问题。
some()方法测试数组中是否至少有一个元素通过提供的函数实现的测试。它返回一个布尔值。
请注意，Array.find 也会在找到目标后结束迭代，但它不支持 IE。
var data = [{"foo":2}, {"foo":19}, {"foo":7}, {"foo":22}]
// if {foo:7} is found, move it to the front and break iteration
data.some((item, idx) =>
item.foo == 7 &&
data.unshift(
// remove the found item, in-place (by index with splice),
// returns an array of a single item removed
data.splice(idx,1)[0]
)
)
// print result
console.log(data)如果您不想改变原始数组，可以这样做：
如果您不想改变原始数组，可以这样做:
var data = [{"foo":2}, {"foo":19}, {"foo":7}, {"foo":22}]
// if {foo:7} is found, move it to to the front and break iteration
const clonedData = [...data]
clonedData.some((item, i, arr) => item.foo == 7 && arr.unshift(item))
// print result
console.log(clonedData)The
findIndex()method returns the index of the first element in the array that satisfies the provided testing function. Otherwise, it returns -1, indicating that no element passed the test.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)<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>If you use lodash and need to have legacy browsers support, use the
_.findIndexmethod:
_.findIndex(data, {foo:19});
这将把键为"foo": 19的数组对象移动到数组的开头。
data.pop()。 - Batmanunshift和splice会进行原地修改。 - vsyncvar collection = [
{
foo: 15,
bar: true
},
{
foo: 19,
bar: false
}
];
function moveToFront(x) {
for (var i = 0; i < collection.length; i++) {
if (collection[i].foo === x) {
collection = collection.splice(i, 1).concat(collection);
break;
}
}
}
moveToFront(19);
console.log(collection);
在每个属性中搜索任何值，第一个匹配成功即停止。由于使用了“some”方法并且在满足条件时打断了对数组的迭代，所以似乎非常快速。
'some'会为数组中存在的每个元素执行回调函数，直到找到其中一个返回true的元素。如果找到这样的元素，则some（）将立即返回true。变异是就地完成的...
var collection = [
{
"foo": 2,
"bar": "test"
},
{
"foo": 19,
"bar": "value"
},
{
"foo": 7,
"bar": "temp"
}
];
function moveToFront(searchValue) {
var idx, exists;
for (idx = 0; idx < collection.length; idx++) {
exists = Object.keys(collection[idx]).some(function (key) {
return collection[idx][key] === searchValue
});
if (exists) break;
}
collection.unshift(collection[idx]);
collection.splice(idx + 1, 1);
}
moveToFront("temp"); // or moveToFront(19); or move whatever
console.log(collection);
另一种解决方案。原地突变...
var collection = [
{
"foo": 2,
"bar": "test"
},
{
"foo": 19,
"bar": "value"
},
{
"foo": 7,
"bar": "temp"
}
];
function moveToFront(property, value, col) {
col.reduce(function (prev, current, idx, obj) {
if (current[property] != value) {
return obj;
} else {
obj.unshift(obj[idx]);
obj.splice(idx + 1, 1);
}
});
}
moveToFront('foo', 7, collection);
console.log(collection);
array.aplicehttps://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Array/splice - Zak