replace and split

Learn to modify strings with .replace and .split.

Replacing with replace

To replace a substring with another you use .replace(search, replacement). "cold-cold".replace("cold", "warm") changes only the first match and returns "warm-cold".

To replace every match you have two options: a regular expression like /cold/g or the .replaceAll() method. "cold-cold".replaceAll("cold", "warm") returns "warm-warm". replace and replaceAll do not modify the original; they return a new string.

Splitting into an array

To break a string into parts you use .split(separator). The string is split wherever the separator appears and the parts are placed in an array. "apple,pear,banana".split(",") returns ["apple", "pear", "banana"].

If the separator is an empty string each character becomes a separate element: "abc".split("") gives ["a", "b", "c"]. split is especially useful for comma-separated values (CSV); you split each line into pieces and reach the fields.

Exercise Split the list into an array

The csv variable holds "Notebook,Pen,Eraser". Declare a variable items and assign the result of csv.split(",") to it. Then print items[0] with console.log. The output on a single line must be Notebook.

Show example solution

const csv = "Notebook,Pen,Eraser";
const items = csv.split(",");
console.log(items[0]);

Test yourself

What is the result of "a-b".replace("-", "/")?
```
"a-b".replace("-", "/")
```
- "a-b"
- "a/b"
- "a/b/c"
- "/"
Show answer

"a/b" — replace changes the first '-' to '/'; the result is "a/b".
Match each method to its job

.replace(x, y)

Changes first match
.replaceAll(x, y)

Changes every match
.split(x)

Splits into array
.slice(a, b)

Takes a part

Write the split call

const line = "a,b,c";
const parts = line____(",");

Show answer

const line = "a,b,c";
const parts = line.split(",");

Next lesson: padStart and trim

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