Javascript 具有多个值的Javascript indexOf方法
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Javascript indexOf method with multiple values
提问by JoeL
I have an arraywich contains multiple same values
我有一个array包含多个相同值的
["test234", "test9495", "test234", "test93992", "test234"]
Here I want to get the index of every test234in the array
在这里我想获取test234数组中每个的索引
For that I've tried Array.prototype.indexOf()method. But It only returns me 0but I want it to return me [0, 2, 4].
为此，我尝试了Array.prototype.indexOf()方法。但它只返回我，0但我希望它返回我[0, 2, 4]。
How can I do that?
我怎样才能做到这一点？
var array = ["test234", "test9495", "test234", "test93992", "test234"];
document.write(array.indexOf("test234"));回答by JoeL
Just make it a for loop to check each array element.
只需让它成为一个 for 循环来检查每个数组元素。
var array = ["test234", "test9495", "test234", "test93992", "test234"];
for (i=0;i<array.length;i++) {
if (array[i] == "test234") {
document.write(i + "<br>");
}
}回答by 4castle
This kind of function doesn't exist built in, but it would be pretty easy to make it yourself. Thankfully, indexOfcan also accept a starting index as the second parameter.
这种功能不存在内置，但自己制作它会很容易。值得庆幸的是，indexOf还可以接受起始索引作为第二个参数。
function indexOfAll(array, searchItem) {
var i = array.indexOf(searchItem),
indexes = [];
while (i !== -1) {
indexes.push(i);
i = array.indexOf(searchItem, ++i);
}
return indexes;
}
var array = ["test234", "test9495", "test234", "test93992", "test234"];
document.write(JSON.stringify(indexOfAll(array, "test234")));回答by Nina Scholz
You can use the fromIndexof Array#indexOf.
您可以使用fromIndex的Array#indexOf。
fromIndex
The index to start the search at. If the index is greater than or equal to the array's length, -1 is returned, which means the array will not be searched. If the provided index value is a negative number, it is taken as the offset from the end of the array. Note: if the provided index is negative, the array is still searched from front to back. If the calculated index is less than 0, then the whole array will be searched. Default: 0 (entire array is searched).
从索引
开始搜索的索引。如果索引大于或等于数组的长度，则返回-1，这意味着不会搜索数组。如果提供的索引值为负数，则将其视为距数组末尾的偏移量。注意：如果提供的索引为负数，数组仍会从前到后搜索。如果计算出的索引小于 0，则将搜索整个数组。默认值：0（搜索整个数组）。
~is a bitwise not operator.
~是按位非运算符。
It is perfect for use with
indexOf(), becauseindexOfreturns if found the index0 ... nand if not-1:value ~value boolean -1 => 0 => false 0 => -1 => true 1 => -2 => true 2 => -3 => true and so on
它非常适合与 一起使用
indexOf()，因为indexOf如果找到索引0 ... n则返回，否则返回-1：value ~value boolean -1 => 0 => false 0 => -1 => true 1 => -2 => true 2 => -3 => true and so on
var array = ["test234", "test9495", "test234", "test93992", "test234"],
result = [],
pos = array.indexOf('test234');
while (~pos) {
result.push(pos);
pos = array.indexOf('test234', pos + 1); // use old position incremented
} // ^^^^^^^
document.write('<pre> ' + JSON.stringify(result, 0, 4) + '</pre>');回答by Paul Kurtis
You may use indexOf with a for loop to get the index values of 0,2,4:
您可以在 for 循环中使用 indexOf 来获取 0,2,4 的索引值：
var array = ["test234", "test9495", "test234", "test93992", "test234"];
let newArr=[];
for (i=0;i<array.length;i++) {
if (array[i].indexOf("test234") >=0 ) {
newArr.push(i);
}
}
document.write(newArr);
回答by ZER0
You can use reduce:
您可以使用减少：
const indexesOf = (arr, item) =>
arr.reduce(
(acc, v, i) => (v === item && acc.push(i), acc),
[]);
So:
所以：
const array = ["test234", "test9495", "test234", "test93992", "test234"];
console.log(indexesOf(array, "test234")); // [0, 2, 4]
An alternative approach could be having an iterator:
另一种方法可能是使用迭代器：
function* finder(array, item) {
let index = -1;
while ((index = array.indexOf(item, index + 1)) > -1) {
yield index;
}
return -1;
}
That's give you the flexibility to have the search in a lazy way, you can do it only when you need it:
这使您可以灵活地以懒惰的方式进行搜索，您可以仅在需要时进行搜索：
let findTest234 = finder(array, "test234");
console.log(findTest234.next()) // {value: 0, done: false}
console.log(findTest234.next()) // {value: 2, done: false}
console.log(findTest234.next()) // {value: 4, done: false}
console.log(findTest234.next()) // {value: -1, done: true}
Of course, you can always use it in loops (since it's an iterator):
当然，你总是可以在循环中使用它（因为它是一个迭代器）：
let indexes = finder(array, "test234");
for (let index of indexes) {
console.log(index);
}
And consume the iterator immediately to generate arrays:
并立即使用迭代器来生成数组：
let indexes = [...finder(array, "test234")];
console.log(indexes); // [0, 2, 4]
Hope it helps.
希望能帮助到你。
