indexOf with multiple arguments

问题

Is it possible to use multiple arguments when determining indexOf on an array?

I want to determine if my array contains any of three integers. Important to note at this stage that the array will only have one value (if it has more, it won't reach this code block).

array.indexOf(123 || 124 || 125) === 0

So if array = [123] then my indexOf should be 0 and therefore true.

If array = [124] then my indexOf should be 0 and therefore true.

What I am finding is happening is [123] works OK but it's not even bothering to check the indexOf for the 2nd or 3rd arguments, and is just returning false.

http://codepen.io/anon/pen/WxmyGp?editors=0011

回答1:

The || operator returns the left hand side if it is true, otherwise it returns the right hand side. 123 || 124 || 125 just means 123.

If you want to test if any of multiple values are in an array, then you have to test each one in turn.

array.indexOf(123) == 0 || array.indexOf(124) == 0 || array.indexOf(125) == 0

Since you only care about one specific index the array, you can turn the whole thing on its head:

[123, 124, 125].indexOf(array[0]) > -1

回答2:

You can do this using Array.some().

The nice thing about this approach is that you will only have to iterate through the array once. If you || multiple indexOf() calls together, you're going to keep iterating the array with every missed search.

function checkArray(array) {
  return array.some(function(item) {
    return item == 123 || item == 124 || item == 125;
  });
};

console.log(checkArray([123, 456, 789]));
console.log(checkArray([456, 789]));
console.log(checkArray([789, 456, 125]));

回答3:

If you want to get multiple results one other way of doing this is Array.prototype.filter(). Bu this will return you the objects itself. If you are interested in the indices then you have to combine it with Array.prototype.reduce() such as;

var a = [1,2,3],
    b = a.filter(e => e === 1 || e === 2)
         .reduce((p,c) => p.concat(a.indexOf(c)),[]);
console.log(b);

来源：https://stackoverflow.com/questions/39000151/indexof-with-multiple-arguments

标签

javascript

arrays

indexof