substring and slice

Learn to take parts of a string with .substring and .slice.

Taking parts with substring

To take a part of a string you use .substring(start, end). start is the start index and end is the end index; end itself is excluded. "welcome".substring(0, 3) returns "wel".

With one argument substring(start) takes from that index to the end: "welcome".substring(3) is "come". substring clamps negative indices to zero; for negative values slice is usually a better fit.

slice and negative indices

.slice(start, end) also takes a part; it resembles substring but supports negative indices. A negative index counts from the end: -1 is the last character, -3 is the start of the last three characters.

For example "welcome".slice(-3) returns the last three letters: "ome". "welcome".slice(0, -2) drops the last two characters: "welc". Thanks to its flexibility slice is a common choice for strings and arrays.

Exercise Take the first three letters

The word variable holds "programming". Declare a variable first and assign the result of word.slice(0, 3) to it. Then print first with console.log. The output on a single line must be pro.

Show example solution

const word = "programming";
const first = word.slice(0, 3);
console.log(first);

Test yourself

Write the substring call

const w = "welcome";
const head = w____(0, 3);

Show answer

const w = "welcome";
const head = w.substring(0, 3);

Match each method to its behavior

.substring(0, 3)

First three chars
.slice(-3)

Last three chars
.substring(3)

From index to end
.slice(0, -2)

Drop last two
What is the result of "welcome".slice(-2)?
```
"welcome".slice(-2)
```
- "me"
- "wel"
- "come"
- "welc"
Show answer

"me" — slice(-2) gives the last two characters: "me".

Next lesson: replace and split

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