Category: JavaScript Answers

Sometimes, we want to fix Uncaught TypeError: this.props.data.map is not a function with React.

In this article, we’ll look at how to fix Uncaught TypeError: this.props.data.map is not a function with React.

How to fix Uncaught TypeError: this.props.data.map is not a function with React?

To fix Uncaught TypeError: this.props.data.map is not a function with React, we can check if this.props.data is an array.

For instance, we write

{
  Array.isArray(this.props.data) &&
    this.props.data.map((e) => {
      //...
    });
}

to call Array.isArray to check if this.props.data is an array.

If it is, then we call this.props.data.map to render the items from the data entries.

Conclusion

To fix Uncaught TypeError: this.props.data.map is not a function with React, we can check if this.props.data is an array.

Sometimes, we want to match multiple occurrences with a regex in JavaScript similar to PHP’s preg_match_all().

In this article, we’ll look at how to match multiple occurrences with a regex in JavaScript similar to PHP’s preg_match_all().

How to match multiple occurrences with a regex in JavaScript similar to PHP’s preg_match_all()?

To match multiple occurrences with a regex in JavaScript similar to PHP’s preg_match_all(), we can use the string matchAll method.

For instance, we write

const regexp = /(?:&|&)?([^=]+)=([^&]+)/g;
const str = "1111342=Adam%20Franco&348572=Bob%20Jones";

for (const match of str.matchAll(regexp)) {
  const [full, key, value] = match;
  console.log(key, value);
}

to call str.matchAll to match the regex for a query string.

We use a for of loop to get all the matches.

In the loop, we get the full string match and the key and value of the query string from the match.

Conclusion

To match multiple occurrences with a regex in JavaScript similar to PHP’s preg_match_all(), we can use the string matchAll method.

Sometimes, we want to increment or decrement for loop by more than one with JavaScript.

In this article, we’ll look at how to increment or decrement for loop by more than one with JavaScript.

How to increment or decrement for loop by more than one with JavaScript?

To increment or decrement for loop by more than one with JavaScript, we can increment with += or decrement with -=.

For instance, we write

for (let i = 0; i < myVar.length; i += 3) {
  //...
}

to increment i by 3 with i += 3.

Or we write

for (let i = myVar.length - 1; i >= 0; i -= 3) {
  //...
}

to decrement i by 3 with i -= 3.

Conclusion

To increment or decrement for loop by more than one with JavaScript, we can increment with += or decrement with -=.

Sometimes, we want to check if a value exists in an object using JavaScript.

In this article, we’ll look at how to check if a value exists in an object using JavaScript.

How to check if a value exists in an object using JavaScript?

To check if a value exists in an object using JavaScript, we use the Object.values and the array includes method.

For instance, we write

const exists = Object.values(obj).includes("test1");

to get an array of property values in object obj with Object.values.

Then we call includes with the value we’re looking for in obj.

Conclusion

To check if a value exists in an object using JavaScript, we use the Object.values and the array includes method.

Sometimes, we want to get the number of digits with JavaScript.

In this article, we’ll look at how to get the number of digits with JavaScript.

How to get the number of digits with JavaScript?

To get the number of digits with JavaScript, we can convert the number to a string.

For instance, we write

const getlength = (number) => {
  return number.toString().length;
};

to define the getLength function that takes a number.

In it, we call toString to convert it to a string.

And then we get the length property of it to get the number of digits of number.

Conclusion

To get the number of digits with JavaScript, we can convert the number to a string.