如何获取当前索引的Array原型图? [英] How to get current index in Array prototype map?
问题描述
function getListings(){
return Array.prototype.map.call(document.querySelectorAll('li.g'),function(e){
return {
rectangle:e.getBoundingClientRect );
}
}
}
然而,我也想要存储这个元素在DOM中出现的顺序,我不知道该怎么做。
我知道我将它存储在数组,并且顺序将是数组的索引,例如:
var listing = getListings();
console.log(listing [0]); // rank#1
console.log(listing [1]); // rank#2
// etc ...
但是我将json对象插入数据库中,存储排名信息的最简单方法是创建一个属性等级在我的对象,但我不知道如何得到我ndex。
某些东西:
function getListings(){
return Array.prototype.map.call(document.querySelectorAll('li.g'),function(e){
return {
rectangle:e.getBoundingClientRect(),
rank: magicFunctionThatReturnsCurrentIndex()//< - 魔术发生
}
}
}
任何帮助指向正确的方向将不胜感激!感谢
MDN文档说:
使用三个参数调用回调:元素的值
元素的索引和正在遍历的数组对象。
所以
function getListings(){
返回Array.pro totype.map.call(document.querySelectorAll('li.g'),function(e,rank){// magic
return {
rectangle:e.getBoundingClientRect(),
rank :排名//< - 魔术发生
}
}
}
I'm using Array.prototype.map.call to store in an array a bunch of node list objects:
function getListings() {
return Array.prototype.map.call(document.querySelectorAll('li.g'), function(e) {
return {
rectangle: e.getBoundingClientRect();
}
}
}
However, I also want to store the order in which this elements appear in the DOM, and I don't know how to do that.
I know that I'm storing this in an array, and the order would be the index of the array. For example:
var listings = getListings();
console.log(listings[0]); // rank #1
console.log(listings[1]); // rank #2
// etc...
but I'm inserting the json object in a database, and the easiest way to store the "rank" information is by creating a property "rank" in my object, but I don't know how to get the "index" of the current array.
Something like:
function getListings() {
return Array.prototype.map.call(document.querySelectorAll('li.g'), function(e) {
return {
rectangle: e.getBoundingClientRect(),
rank: magicFunctionThatReturnsCurrentIndex() // <-- magic happens
}
}
}
Any help pointing me to the right direction will be greatly appreciated! Thanks
The MDN documentation says:
callback is invoked with three arguments: the value of the element, the index of the element, and the Array object being traversed.
So
function getListings() {
return Array.prototype.map.call(document.querySelectorAll('li.g'), function(e, rank) { // magic
return {
rectangle: e.getBoundingClientRect(),
rank: rank // <-- magic happens
}
}
}
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