Why am I receiving the error message 'Uncaught TypeError: results is not a function' while utilizing the map function?

Question

Why am I receiving the error message 'Uncaught TypeError: results is not a function' while utilizing the map function?

Struggling to grasp the concept of the map function and puzzled by why my output is showing

[undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined]

, even though I've provided the correct this value as per the documentation...

var numbers = [1,2,3,4,5,6,7,8];

var results = numbers.map(
  function(foo){
  console.log(foo * foo);
 }, results
);
results();

Any insights would be greatly appreciated!

javascript

Answer 1

Answer №1

When using the map() method, ensure that the function you pass to it returns the desired result.

var numbers = [1, 2, 3, 4, 5, 6, 7, 8];

var results = numbers.map(function(num) {
  return num * num; 
}); 

console.log(numbers);

If your function does not explicitly return a value, it will default to returning undefined after each execution.

As stated in the documentation for Array.prototype.map():

The map() method generates a new array by applying a provided function to every element of the original array.

Answer 2

When using the map() method, ensure that the function you pass to it returns the desired result.

var numbers = [1, 2, 3, 4, 5, 6, 7, 8];

var results = numbers.map(function(num) {
  return num * num; 
}); 

console.log(numbers);

If your function does not explicitly return a value, it will default to returning undefined after each execution.

As stated in the documentation for Array.prototype.map():

The map() method generates a new array by applying a provided function to every element of the original array.

Answer 3

Answer №2

Check out this simplified approach:

let nums = [1,2,3,4,5,6,7,8];

const displayValues = (info) => {
    console.log(info)
    return info;
}

nums.map(displayValues);

Answer 4

Check out this simplified approach:

let nums = [1,2,3,4,5,6,7,8];

const displayValues = (info) => {
    console.log(info)
    return info;
}

nums.map(displayValues);

Answer 5

Answer №3

What causes the error 'Uncaught TypeError: results is not a function' to appear when using the map function?

This error occurs because the Array.prototype.map method will never output a function.

15.4.4.19 Array.prototype.map ( callbackfn [ , thisArg ] )

The parameter callbackfn should be a function that takes three arguments. When the map function is called, it iterates through each element in the array, executing the provided function and constructing a new Array from the returned values.

Answer 6

What causes the error 'Uncaught TypeError: results is not a function' to appear when using the map function?

This error occurs because the Array.prototype.map method will never output a function.

15.4.4.19 Array.prototype.map ( callbackfn [ , thisArg ] )

The parameter callbackfn should be a function that takes three arguments. When the map function is called, it iterates through each element in the array, executing the provided function and constructing a new Array from the returned values.

Why am I receiving the error message 'Uncaught TypeError: results is not a function' while utilizing the map function?

Answer №1

Answer №2

Answer №3

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