Syntax, Parameter and Return Value
Syntax:
_.startsWith([string=''], [target], [position=0])
Parameters:
-
[string=''] (string): The string to inspect.
-
[target] (string): The string to search for.
- [position=0] (number): The position to start the search at.
Return Value:
(boolean) - Returns true if string starts with target, else false.
Examples
Checking for a Specific Prefix in a String:
JavaScript
var _ = require('lodash');
var text = 'hello world';
console.log(_.startsWith(text, 'hello'));
You can also try this code with Online Javascript Compiler
Output:
true
Demonstrates checking if a string starts with a specific word.
Validating URL Protocols:
JavaScript
var url = 'https://www.example.com';
console.log(_.startsWith(url, 'https'));
You can also try this code with Online Javascript Compiler
Output:
true
Shows how to validate the protocol of a URL.
Searching from a Specific Position:
JavaScript
var sentence = 'This is a test';
console.log(_.startsWith(sentence, 'is', 2));
You can also try this code with Online Javascript Compiler
Output:
true
An example of using the position parameter to check for a substring starting at a specific index in the string.
Filtering Data Based on Prefix:
JavaScript
var filenames = ['report.txt', 'image.jpg', 'script.js'];
var txtFiles = filenames.filter(name => _.startsWith(name, 'report'));
console.log(txtFiles);
You can also try this code with Online Javascript Compiler
Output:
['report.txt']
Demonstrates filtering an array of strings based on a prefix.
Frequently Asked Questions
How does _.startsWith() differ from using String.prototype.startsWith()?
_.startsWith() is Lodash's implementation and is similar to JavaScript's native startsWith() method. The primary difference is that Lodash methods like _.startsWith() can be chained with other Lodash utilities for more complex operations.
Can _.startsWith() handle case-sensitive checks?
_.startsWith() is case-sensitive. For case-insensitive checks, you should convert both the string and target to the same case (e.g., using .toLowerCase()).
Is _.startsWith() suitable for checking multiple possible starts?
For multiple starts, _.startsWith() would need to be used in conjunction with other methods, like Array.prototype.some(), to check each potential start string.
Conclusion
Lodash's _.startsWith() method is an effective tool for verifying whether a string begins with a specified substring. It's particularly useful for string validation, searching, and filtering tasks where the start of the string is significant.
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