如何迭代(对于 obj 中的键)起始中间位置

Question

我有一个obj：

let obj = {
1: 'one',
2: 'two',
3: 'three',
7: 'seven'
}

是否有机会从 3 个位置开始迭代它，如下所示：

for (let key = 3 in obj) {
console.log(obj[key]) // An output will be 'three' and 'seven'
}

我需要以最快的方式做到这一点，因为 obj 非常大

Answer 1

只需通过简单的方式进行操作即可。

let obj = {
1: 'one',
2: 'two',
3: 'three',
7: 'seven'
};
// make sure that your case is in order
// get keys of your object
const keys = Object.keys(obj);
// find index of starting key
const index = keys.indexOf('3');
// make sure index >= 0
// each all keys from starting key to the end by old school way
for (let i = index; i < keys.length; i++) {
var key = keys[i];
console.log(obj[key]);
}

Answer 2

如果键小于3，您可以使用continue跳过迭代：

let obj = {
1: 'one',
2: 'two',
3: 'three',
7: 'seven'
};
for(let [key, val] of Object.entries(obj)){
if(key < 3 ){
continue;
}
console.log(val);
}

Answer 3

您可以通过多种方式实现此目的。一种算法涉及将对象转换为数组。然后确定中点。

let obj = {
1: 'one',
2: 'two',
3: 'three',
7: 'seven'
}
Object.entries(obj).forEach(([key, value], index, array) => {
const split = array.length/2
const midPoint = split % 2 == 0 ? split : Math.floor(split)
if(index >= midPoint){
console.log(key)
}
})