Consider following code:
var arr = [111, 222, 333];
for(var i in arr) {
if(i === 1) {
// Never executed
}
}
It will fail, because typeof i === 'string'.
Is there way around this? I could explicitly convert i to integer, but doing so seems to defeat the purpose using simpler for in instead of regular for-loop.
Edit:
I am aware of using == in comparison, but that is not an option.
You have got several options
Make conversion to a Number:
parseInt(i) === 1
~~i === 1
+i === 1
Don't compare a type (Use == instead of ===):
i == 1 // Just don't forget to add a comment there
Change the for loop to (I would do this but it depends on what you are trying to achieve):
for (var i = 0; i < arr.length; i++) {
if (i === 1) { }
}
// or
arr.forEach(function(item, i) {
if (i === 1) { }
}
By the way you should not use for...in to iterate through an array. See docs: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in
for..in should not be used to iterate over an Array where index order is important. Array indexes are just enumerable properties with integer names and are otherwise identical to general Object properties. There is no guarantee that for...in will return the indexes in any particular order and it will return all enumerable properties, including those with non–integer names and those that are inherited.
Because the order of iteration is implementation dependent, iterating over an array may not visit elements in a consistent order. Therefore it is better to use a for loop with a numeric index (or Array.forEach or the non-standard for...of loop) when iterating over arrays where the order of access is important.
for in for arrays. It seems to be too easy to break unexpectedly.
forEach is a good replacement. Simple and also faster solution than for...i. You should use for...i only if you need to iterate trough an object.
With === you compare also the type of values. Use == instead:
if ( i == 1 ) {}
or cast i to integer:
if ( +i === 1 ) {}
Also you can try with 'standard' for loop:
for (var i = 0; i < arr.length; i++) {
if (i === 1) {}
}
If you don't need browser support below IE9, you can use Array.forEach
If you do, use the good ol' for (i = 0; i < arr.length; i++) {} loop.
Is this what you mean?
var arr = [1, 2, 3];
for(var i in arr) { //i is not the value of an element of the array, but its "attribute name"
if(arr[i] === 1) {
}
}
In any case, I'd use the good old classic for syntax, it's the recommended way to deal with arrays
for-in loops properties in object, you could use for-of to loop array.
for (const i in [11, 22, 33, 44, 55]) {
console.log(`${typeof i}: ${i}`);
}
string: 0
string: 1
string: 2
string: 3
string: 4
const obj = {
11: 'a',
22: 'b',
33: 'c',
44: 'd',
55: 'e',
}
for (const i in obj) {
console.log(`${typeof i}: ${i} -> ${obj[i]}`);
}
string: 11 -> a
string: 22 -> b
string: 33 -> c
string: 44 -> d
string: 55 -> e
for (const i of [11, 22, 33, 44, 55]) {
console.log(`${typeof i}: ${i}`);
}
number: 11
number: 22
number: 33
number: 44
number: 55
==so no type check will be includedforloop for iterating arrays.iand why is a Stringfor…inenumerations on arrays! Just because a hammer is a simpler tool than an electric screwdriver, you shouldn't use it for screws.