Extracting substrings

TypeScript:
Extracting substrings

How to:

In TypeScript, you slice and dice strings with methods like substring(), slice(), and the ES6 includes() for finding text within strings.

let fullString: string = "Hello, TypeScript enthusiasts!";

// Grab from character 7 to 18
let substr: string = fullString.substring(7, 18);
console.log(substr); // Outputs: TypeScript

// Same deal but with slice()
let sliced: string = fullString.slice(7, 18);
console.log(sliced); // Outputs: TypeScript

// Check if a substring exists
let exists: boolean = fullString.includes("TypeScript");
console.log(exists); // Outputs: true

Deep Dive

Once upon a time, string manipulation was more awkward—think C’s string functions. Now, JavaScript and TypeScript offer methods that handle Unicode, respect character encoding, and work directly with string objects. substring() and slice() are similar but with a twist: slice() can take negative indices, retroactively counting from the end. substring() treats them as zeros. In performance-sensitive situations, picking one over the other can matter, but for day-to-day use, it’s pretty much six of one, half a dozen of the other.

// Using negative index with slice
let endSliced: string = fullString.slice(-25, -7);
console.log(endSliced); // Outputs: Hello, Type

As for includes(), it’s a boon for readability over the classic indexOf(), making your intentions clear at a glance. No more if (string.indexOf('some text') !== -1); just a straightforward if (string.includes('some text')).

TypeScript:Extracting substrings

How to:

Deep Dive

See Also

TypeScript:
Extracting substrings