isString()

isString(value): value is string

Checks if a value is a string.

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Parameters

value: unknown

The value to check.

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Returns: value is string

true if the value is a string, false otherwise.

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Since

1.0.0

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Example

isString('hello');       // => true
isString('');            // => true
isString(String(123));   // => true
isString(123);           // => false
isString(null);          // => false
isString(new String()); // => false (String object)

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How it works?

Type guard that checks if a value is a string.

Type Narrowing

Common Checks

Value	Result
'hello'	true
''	true
`template`	true
String(123)	true
new String('hello')	false (boxed)
123	false
['h', 'i']	false

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Use Cases

Validate text input 📌

Ensure a value is a string before manipulation. Essential for form handling and text processing.

#validate#string#text#input#manipulation#forms

if (isString(input)) {
  const trimmed = input.trim();
  saveToDatabase(trimmed);
}

Filter strings from mixed arrays

Extract string values from arrays containing mixed types.

#filter#strings#mixed#arrays#extraction#types

const values = ["hello", 42, "world", null, true];
const strings = values.filter(isString);
// strings: string[] = ["hello", "world"]