If I run this, I will get 1, 2, ..., 50 in my console.
keys = [1, 2, 3, ..., 50];
async.forEach(keys, function (key, callback){
console.log(key);
callback();
}
But I want to have an step of 3. I want to get: 1, 4, 7, ... like this for loop:
for (let key = 1; key <= 50; key = key + 3) {
}
How can I achieve this with async?
I'm not sure what async.forEach is, but assuming you're just trying to do a normal forEach with 3 steps as you said, here's my approach:
forEach is not really appropriate for usages where you manipulate your index (specially in more hardcore cases, where your index might change within the loop), but as a quick hack, you can do the following:
keys.forEach((key, index) => {
if(index % 3 === 0) {
// Only true when it's a multiple of 3
// Do your loop body
}
});
Note that forEach takes a callback, where the first parameter is the current value, and optional parameters (among which is the current index), see the docs
const res = keys.reduce((acc, elem, i) => i % 3 == 0 ? [...acc, elem] : acc, []);
Will give you the result res of:
[1, 4, 7, 10, 13, ..., 48]; // Every 3rd index
Where i % 3 controls the step. So, if you want to increment by 4 each time you could change this to i % 4 etc...
Thus, you can use this in your code like so:
keys = [1, 2, 3, ..., 50];
let stepKeys = keys.reduce((acc, elem, i) => i % 3 == 0 ? [...acc, elem] : acc, []);
async.forEach(stepKeys, function (key, callback){
console.log(key);
callback();
}
keysis set to[1, 2, 3...initially, just multiply by 3 and subtract to get to1, 4, 7on each iteration? Is that what you mean?