isString

Determine if a value is a string type.

API

isString

Return

Argument	Description	Type
boolean	Whether it is a string	boolean

Parameters

Parameter	Description	Type	Default
obj	Value to check	unknown	Required

Example

Basic Usage

import { isString } from 'ranuts';

console.log(isString('hello')); // true
console.log(isString(123)); // false
console.log(isString(null)); // false
console.log(isString(undefined)); // false

Type Checking

import { isString } from 'ranuts';

function processValue(value) {
  if (isString(value)) {
    console.log('Is string:', value.toUpperCase());
  } else {
    console.log('Not a string');
  }
}

processValue('hello'); // 'Is string: HELLO'
processValue(123); // 'Not a string'

Parameter Validation

import { isString } from 'ranuts';

function validateInput(input) {
  if (!isString(input)) {
    throw new Error('Input must be a string');
  }
  return input.trim();
}

Notes

1. Type detection: Uses Object.prototype.toString.call() for precise type detection.
2. Strictness: Only returns true when value is a true string type, other types (including string objects) return false.
3. Use case: Commonly used for type checking, parameter validation, etc.