Using the some array helper in ES6

ES6 comes with a number of helper methods that can be applied to arrays. One of these is called some which returns true if at least one element in an array fulfils the specified condition and false otherwise. If you’re familiar with C# and LINQ then the some function is very similar to the Any 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"},
]

We want to find out if there’s any programmer in the array who writes C++:

let anyCplusPlus = programmers.some(function(prog) {
  return prog.language === 'C++'
})

Some accepts a function which in turn operates on a single member of the array which some is applied to. Some iterates through each member in the array and calls the function that was provided to it. The function must return a value otherwise the result, “anyCplusPlus” will always be false due to the null returned from the function. Null is a falsy JS value so anyCplusPlus will also be false. If at least one programmer element matches the condition then anyCplusPlus will be true, which is in fact the case in our example.

We have no Python programmers in the array so the following will return false:

let anyPython = programmers.some(function(prog) {
  return prog.language === 'Python'
})