Solve - map is not a function Error in JavaScript

Solve - map is not a function Error #

The "TypeError: map is not a function" occurs when we call the map() method on an object that is not an array. To solve the error, console.log the value you're calling the map() method on and make sure to only call the map method on valid arrays.

Here is an example of how the error occurs.

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const obj = {};

// ⛔️ Uncaught TypeError: map is not a function
const result = obj.map(element => {
  return element + 1;
});

We called the Array.map() method on an object and got the error back.

To solve the error, console.log the value you're calling the map method on and make sure it's a valid array.

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const arr = [1, 2, 3];

const result = arr.map(element => {
  return element + 1;
});

console.log(result); // 👉️ [2, 3, 4]

You can conditionally check if the value is an array by using the Array.isArray method.

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const arr = 'test';

const result = Array.isArray(arr) ? arr.map(element => element + 1) : [];

console.log(result); // 👉️ []

We used a ternary operator, which is very similar to an if/else statement.

If the value is an array, we return the result of calling the map method on it, otherwise we return an empty array. This way, you won't get an error, even if the value is not an array.

If you have an array-like object which you're trying to convert to an array before calling the map method, use the Array.from method.

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const set = new Set([1, 2, 3]);

const result = Array.from(set).map(element => element + 1);
console.log(result); // 👉️ [2, 3, 4]

Before calling the map method, we convert the value to an array. This would also work for array-like objects like the NodeList returned from calling the getElementsByClassName method.

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{Array.isArray(value) ? (value).map(e => /* your code */) : null}

We used a ternary operator to check if the value is an array.

If it is an array, we return the result of calling the map() method on it, otherwise we return a null value.

Further Reading #

• Filter an Array with Multiple Conditions in JavaScript
• Filter an Array of Objects based on a property - JavaScript
• Check if Array has all Elements of Another Array - JavaScript
• Check if Array Contains an Object in JavaScript
• Check if Array of Strings contains a Substring in JS