substring

Learn to take parts of a string with substring.

substring

To take a part of a String you use the .substring(start, end) method. start is inclusive, end is exclusive: "DartLang".substring(0, 4) returns "Dart". Indexing is zero-based.

If you omit the second parameter it goes to the end of the String: "DartLang".substring(4) returns "Lang". Negative indices are not supported; keep indices within the String length to avoid errors.

Start and end rules

In substring the start index exists in the string and is included in the result. The end index is excluded; it means "take up to here". "welcome".substring(0, 3) takes the letters w, e, l and returns "wel".

Both parameters must be between 0 and length. start cannot be greater than end; otherwise an error is thrown. Practical tip: the number of characters taken is end - start.

Exercise Take the first 4 characters

Declare a String variable word with the value "DartLang". Declare a new variable first and assign the result of word.substring(0, 4) to it. Then print first with print(first);. The output on a single line must be Dart.

Show example solution

String word = "DartLang";
var first = word.substring(0, 4);
print(first);

Test yourself

Match the call to its meaning

substring(0, 3)

First 3 characters
substring(2)

From index 2 to end
substring(0, 1)

First character
substring(1, 3)

Middle part

Write the substring call

String word = "Dart";
print(word____);

Show answer

String word = "Dart";
print(word.substring(0, 3));

What does "welcome".substring(0, 3) return?
```
"welcome".substring(0, 3)
```
- "welc"
- "w"
- "lco"
- "wel"
Show answer

"wel" — substring(0, 3) takes indices 0, 1, 2: wel.

Next lesson: contains and indexOf

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