prelude

The standard module for functional programming.

What

A minimalist collection of functions to support functional programming.

For example, it includes the following:

Method as function

Method as function

If you wanted to apply trim to all elements of a string[], you would do something like this:

const runtime = [" deno ", " node.js"].map((v) => v.trim());

Use string#trim.

import { trim } from "https://deno.land/x/prelude_js@$VERSION/trim.ts";
const runtime = [" deno ", " node.js"].map(trim);

trim

Removes the leading and trailing white space and line terminator characters from a string.

import { trim } from "https://deno.land/x/prelude_js@$VERSION/trim.ts";
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

assertEquals(trim(" deno "), "deno");

trimStart

Removes the leading white space and line terminator characters from a string.

import { trimStart } from "https://deno.land/x/prelude_js@$VERSION/trim_start.ts";
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

assertEquals(trimStart(" deno "), "deno ");

trimEnd

Removes the trailing white space and line terminator characters from a string.

import { trimEnd } from "https://deno.land/x/prelude_js@$VERSION/trim_end.ts";
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

assertEquals(trimEnd(" deno "), " deno");

toUpperCase

Converts all the alphabetic characters in a string to uppercase.

import { toUpperCase } from "https://deno.land/x/prelude_js@$VERSION/to_upper_case.ts";
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

assertEquals(toUpperCase("deno"), "DENO");

toLowerCase

Converts all the alphabetic characters in a string to lowercase.

import { toLowerCase } from "https://deno.land/x/prelude_js@$VERSION/to_lower_case.ts";
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

assertEquals(toLowerCase("Deno"), "deno");

head

Returns the first element of the given Iterable.

import { head } from "https://deno.land/x/prelude_js@$VERSION/head.ts";
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

assertEquals(head(""), "");
assertEquals(head("abc"), "a");
assertEquals(head([]), undefined);
assertEquals(head([1, 2, 3]), 1);
assertEquals(head(new Set(["x", "y", "z"])), "x");

last

Returns the last element of the given Iterable.

import { last } from "https://deno.land/x/prelude_js@$VERSION/last.ts";
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

assertEquals(last(""), "");
assertEquals(last("abc"), "c");
assertEquals(last([]), undefined);
assertEquals(last([1, 2, 3]), 3);
assertEquals(last(new Set(["x", "y", "z"])), "z");

Where is mod?

There is no single entry point such as mod.

This prevents the inclusion of many unnecessary modules.

License

Released under the MIT license