CODEWITHSUNDEEP
javascriptloopslodash
Temp O'rary
Temp O'rary

Reputation: 5808

lodash : how to loop with between a start value and end value

I've a for loop in javascript shown below. How to convert it to lodash for loop? In such scenarios using lodash is advantageous over javascript for loop?

I've not used lodash much. Hence please advice. 

for (var start = b, i = 0; start < end; ++i, ++start) {
// code goes here
}

Upvotes: 11

Views: 27473

Answers (3)

Andrei L
Andrei L

Reputation: 3651

You can use lodash range
https://lodash.com/docs/4.17.4#range

_.range(5, 10).forEach((current, index, range) => {
    console.log(current, index, range)
})

// 5, 0, [5, 6, 7, 8, 9, 10]
// 6, 1, [5, 6, 7, 8, 9, 10]
// 7, 2, [5, 6, 7, 8, 9, 10]
// 8, 3, [5, 6, 7, 8, 9, 10]
// 9, 4, [5, 6, 7, 8, 9, 10]
// 10, 5, [5, 6, 7, 8, 9, 10]

Upvotes: 13

IxDay
IxDay

Reputation: 3707

I will imagine that b = 3 and end = 10 if I run your code and print the variables here is what I will get:

var b = 3;
var end = 10;

for (var start = b, i = 0; start < end; ++i, ++start) {
  console.log(start, i);
}

> 3 0
> 4 1
> 5 2
> 6 3
> 7 4
> 8 5
> 9 6

To perform this with lodash (or underscore) I will first generate an array with range then iterate over it and gets the index on each iteration.

Here is the result

var b = 3;
var end = 10;

// this will generate an array [ 3, 4, 5, 6, 7, 8, 9 ]
var array = _.range(b, end); 

// now I iterate over it
_.each(array, function (value, key) {
  console.log(value, key);
});

And you will get the same result. The complexity is the same as the previous one (so no performance issue).

Upvotes: 7

Binkan Salaryman
Binkan Salaryman

Reputation: 3048

It seems there is no lodash way for writing loose for loops (those not iterating over a collection), but here is a simplified version of it:

for (var i = 0; i < end - b; i++) {
      var start = i + b;
      // code goes here
}

Upvotes: 0

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