.forEach(), .map(), .filter() .... What's the difference?

.forEach:

.forEach(), is used to execute the same code on every element in an array but does not change the array and it returns undefined.

Example:
In the example below we would use .forEach() to iterate over an array of food and log that we would want to eat each of them.

let food = ['mango','rice','pepper','pear'];
food.forEach(function(foodItem){
    console.log('I want to eat '+foodItem);
});

Running this on your console;

.map():
.map() executes the same code on every element in an array and returns a new array with the updated elements.

Example:
In the example below we would use .map to iterate over the elements of the cost array and divide each element by 10, then assign our new array containing the new cost to the variable newCost.

let cost = [100,400,300,700];
let newCost = cost.map(function(costItem){
    return costItem / 10;
});
console.log(newCost);

Running this on your console;

.filter():
.filter() checks every element in an array to see if it meets a certain criteria and returns a new array with the elements that return truthy for the criteria.

Example:
In the example below we would use .filter to return values that are less than 200.

let cost = [100,400,50,40,700];
let smallCost = cost.filter(function(costItem){
    return costItem < 200
});
console.log(smallCost);

Running this on your console;

That's all folks...

Comments

[Patrick Tingen]

Guys? ;)

[Johnson Ogwuru]

Urhmmmmm.. Lol

[Patrick Tingen]

It was a bit tongue in cheek, and I don't want to be too PC, but it's these small things that could make a (small) difference.

That's all, folks 😇

[Nick Gattuso]

You're being too PC lol. Great article ogwuru.

[Johnson Ogwuru]

Thanks nick

[Roman Gusev]

Are you assuming that only guys can be interested in higher-order functions?

[Johnson Ogwuru]

Nope, not at all

[IsaacLeimgruber]

Lmao what is this triggered question pls

[Ali Abbas]

Absolute Knowledge. Great Article Dev

[Johnson Ogwuru]

Thanks, glad you enjoyed it.

[Andrew Tanner 🇪🇺]

Simple. Love it! Now I know what Map and Filter do.

[Johnson Ogwuru]

I'm happy you loved it. Thanks

[IsaacLeimgruber]

Fold_left/Fold_right some days?

[zain]

simple and clean, thanks a lot

[Let's Code]

i agreed

[Let's Code]

These are definitely essential knowledge engineers have to know. Would add a supplemental video on top of this post.