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denoland-deno/std/strings/pad.ts
2020-01-02 15:13:47 -05:00

75 lines
2.2 KiB
TypeScript

// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
/** FillOption Object */
export interface FillOption {
/** Char to fill in */
char?: string;
/** Side to fill in */
side?: "left" | "right";
/** If strict, output string can't be greater than strLen*/
strict?: boolean;
/** char/string used to specify the string has been truncated */
strictChar?: string;
/** Side of truncate */
strictSide?: "left" | "right";
}
/**
* Pad helper for strings.
* Input string is processed to output a string with a minimal length.
* If the parameter `strict` is set to true, the output string length
* is equal to the `strLen` parameter.
* Example:
*
* pad("deno", 6, { char: "*", side: "left" }) // output : "**deno"
* pad("deno", 6, { char: "*", side: "right"}) // output : "deno**"
* pad("denosorusrex", 6 {
* char: "*",
* side: "left",
* strict: true,
* strictSide: "right",
* strictChar: "..."
* }) // output : "den..."
*
* @param input Input string
* @param strLen Output string lenght
* @param opts Configuration object
* @param [opts.char=" "] Character used to fill in
* @param [opts.side="left"] Side to fill in
* @param [opts.strict=false] Flag to truncate the string if length > strLen
* @param [opts.strictChar=""] Character to add if string is truncated
* @param [opts.strictSide="right"] Side to truncate
*/
export function pad(
input: string,
strLen: number,
opts: FillOption = {
char: " ",
strict: false,
side: "left",
strictChar: "",
strictSide: "right"
}
): string {
let out = input;
const outL = out.length;
if (outL < strLen) {
if (!opts.side || opts.side === "left") {
out = out.padStart(strLen, opts.char);
} else {
out = out.padEnd(strLen, opts.char);
}
} else if (opts.strict && outL > strLen) {
const addChar = opts.strictChar ? opts.strictChar : "";
if (opts.strictSide === "left") {
let toDrop = outL - strLen;
if (opts.strictChar) {
toDrop += opts.strictChar.length;
}
out = `${addChar}${out.slice(toDrop, outL)}`;
} else {
out = `${out.substring(0, strLen - addChar.length)}${addChar}`;
}
}
return out;
}