Using the forEach array helper in ES6

ES6 comes with a number of helper methods that can be applied to arrays. One of these is called forEach which applies a function on each member of an array. If you’re familiar with C# and LINQ then the forEach array helper is very similar to the ForEach LINQ extension method.

Let’s see an example.

We have the following group of programmers:

let programmers = [
  	 {"name":"John","age":20,"language":"C#"},
     {"name":"Mary","age":24,"language":"Java"},
     {"name":"Jane","age":25,"language":"C++"},
     {"name":"Peter","age":22,"language":"JavaScript"},
     {"name":"Fred","age":21,"language":"C++"},
     {"name":"Sophie","age":28,"language":"C#"},
     {"name":"James","age":27,"language":"Java"},
     {"name":"Charlotte","age":26,"language":"Java"},
]

Say we want print the content of each programmer object in the console. The following example shows how to solve that using the forEach helper:

programmers.forEach(function(prog) {
  console.log(`Name: ${prog.name}, age: ${prog.age}, language: ${prog.language}`)
})

Here’s an example of the output:

Name: John, age: 20, language: C#

forEach accepts a function which in turn operates on a single member of the array which forEach is applied to. forEach iterates through each member in the array and calls the function that was provided to it. Unlike many other array helpers in ES6, forEach doesn’t return anything. It performs an action on an array element and continues until the end of the array.

We can use forEach to collect all names from the programmers array. We could use the “map” array helper as well, but this will do for demo purposes:

let names = []
programmers.forEach(function(prog) {
  names.push(prog.name)
})

Here’s the names array:

["John","Mary","Jane","Peter","Fred","Sophie","James","Charlotte"]

View all posts related to JavaScript here.

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About Andras Nemes
I'm a .NET/Java developer living and working in Stockholm, Sweden.

2 Responses to Using the forEach array helper in ES6

  1. Geoff Hirst says:

    Andras, on a slight tangent what is most efficient, ToArray or ToList? Or does it depend on project?

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