replacing-text-in-strings.md

Replacing Text In Strings

• Author: funnyboy-roks

Strings can often have text in them that you don't want to be the same, for example, replaceing new lines with commas, or removing all occurances of a certain character.

Information

Reference Material:

• MDN

Examples and Explanation

We can do a simple String.replace() for the first occurance of a string in another string using the following:

let myString = 'I think JavaScript is very fun!';

myString = myString.replace('think', 'know');
//                          Original Replace

console.log(myString); // 'I know JavaScript is very fun!'

This is very useful if you're wanting to replace a single occurance, however, most of the time we want to do all occurances. To do this, we need to use a Regular Expression, like so

let myString = 'The dog jumped over the cat. The cat did not like the dog, so the cat ran from the dog.';

myString = myString.replace(/dog/g, 'ferret'); // In order to replace globally, we need to use the regular expression `g` flag.

console.log(myString); // 'The ferret jumped over the cat. The cat did not like the ferret, so the cat ran from the ferret'

We can also use a lambda function instead of the replacement string. This can be useful if we want to replace with different values based on the text.

let myString = 'The dog jumped over the cat. The cat did not like the dog, so the cat ran from the dog.';

myString = myString.replace(/(dog|cat)/g, (str) => {
    switch (str) {
        case 'dog':
            return 'ferret';
        case 'cat':
            return 'fox';
    }
});

console.log(myString); // 'The ferret jumped over the fox. The fox did not like the ferret, so the fox ran from the ferret.'