Strings, Numbers & Math›Extra· 30 min read

String Methods

Built-in tools to measure, change, search and slice text.

What you will learn

Use common string methods
Search within strings
Transform text

The everyday methods

Method	Does
`.length`	Number of characters
`.toUpperCase()` / `.toLowerCase()`	Change case
`.includes("x")`	Does it contain x? (true/false)
`.indexOf("x")`	Position of x (or -1)
`.slice(0, 3)`	Cut out part of the text
`.replace("a","b")`	Replace text
`.trim()`	Remove spaces at the ends
`.split(",")`	Break into an array

Below, text has deliberate extra spaces at both ends. We use a few methods on it and print the results.

Chaining string methods

<script>
  let text = "  CodingClave  ";
  document.write(text.trim().toUpperCase() + "<br>");
  document.write("Length: " + text.trim().length + "<br>");
  document.write("Has 'Clave'? " + text.includes("Clave"));
</script>

Live preview

Line by line: text.trim() removes the surrounding spaces (giving "CodingClave"), then .toUpperCase() shouts it in capitals. text.trim().length counts the characters after trimming — 11. text.includes("Clave") asks "is the word Clave in there?" and answers true.

Note: Output: CODINGCLAVE Length: 11 Has 'Clave'? true

Tip: Methods can be chained: text.trim().toUpperCase() trims first, then upper-cases the result. Read left to right.

Q. Which method removes spaces from the start and end of a string?

Answer: .trim() removes leading and trailing whitespace — very common when handling form input.

✍️ Practice

Take a messy string with extra spaces and clean + uppercase it.
Use .split(",") to turn "a,b,c" into an array.

🏠 Homework

Write a function that takes a full name and returns the initials (hint: split + slice).