theming-log

Creates a logger with theme for text decorations.

Usage

const themingLog = require('theming-log');
const ansiColors = require('ansi-colors'); // Use ansi-colors for coloring in this example.

const emojiCry = String.fromCodePoint(0x1f622);

const theme = {
  ERROR: '{red: {1}}',
  red: ansiColors.red,
  emoji: {
    Cry: () => emojiCry,
  },
};

const log = themingLog(theme);

log('{emoji.Cry} This is {ERROR: an error message: {1: error code} }.', 'E001');
// => '😢 This is \u001b[31man error message: E001\u001b[39m.'

var str = themingLog.format(
  '{emoji.Cry} This is {ERROR: an error message: {1: error code} }.',
  'E001'
);
// str === '😢 This is \u001b[31man error message: E001\u001b[39m.'

API

themingLog(theme [, logger] [, lineSep]) : function

Creates a logging function based on console.log or a specified logging function. This created logging function converts a template text which contains style blocks (for example, '{MSG: a message.}') to a decorated text.

The theme is an plain object which maps pairs of a style name ('MSG' in the above example) and either a style function or a template text. A style function receives a block content ('a message' in the above example) and returns a converted text. If a block content is a template text, it is parsed and converted with theme equally.

If the 2nd or 3rd argument is boolean, it is set to lineSep. If lineSep is true, the created logging function split a converted text into multiple lines with newline codes and output them line by line.

Parameters:

| Parameter | Type | Description | | :-------- | :------: | :---------------------------------------------------------------------------------------------------------------------- | | theme | object | An object which is a map of style names and either style functions or template texts. | | logger | function | A logging function which is based on by a created logging function. (Optional, and console.log in default.) | | lineSep | boolean | If true, A logging function split a converted text into multiple lines with newline codes and output them line by line. |

Returns:

A logging function with theme for text decorations.

The API of a returned function is as follows:

• log (template [, ...args]) : Void

  | Parameters | Type | Description | | :--------- | :----: | :-------------------------------------------------------- | | template | string | A template text (explained above) | | args | any | Style blocks for arguments (explained above) |

Format of a template text

A template text can contain style blocks in itself. A style block is rounded by { and }, and this can has a pair of a style name and a block content which are separated by a colon :. If there is no colon in a style block, the whole text in the block is operated as a style name.

• '{ xxxx: yyyy }' → the style name is 'xxxx' and the block content is 'yyyy'.
• '{ xxxx }' → the style name is 'xxxx' and the block content is ''.
• '{ xxxx : }' → the style name is 'xxxx' and the block content is ''.
• '{ : yyyy }' → 'yyyy' is operated as a text, not a block content.

Texts in a style block, both a style name and a block content, are trimmed white spaces on both sides. Regarding a block content, the escape mark \ can prevent trimming. Also, this mark can escape { and }.

• '{ xxx: \\ yyy\\ }' → theme name is 'xxx' and block content is ' yyy '.
• '\\{ xxx: yyy \\}' → a text '{ xxx: yyy }', not a style block.

NOTICE: Both a function created by themingLog and themingLog.format use \ as an escape mark, therefore \ in a template text are erased. So you need to take care of \ marks, especially path separators on Windows.

var log = themingLog({}, console.log);
var format = themingLog.format;

// Erases '\\' as a escape mark.
log('C:\\\\abc\\\\def\\\\ghi');
// => console.log('C:\\abc\\def\\ghi') => C:\abc\def\ghi

// Not erases '\\' in arguments.
log('{1}', 'C:\\abc\\def\\ghi');
// => console.log('C:\\abc\\def\\ghi') => C:\abc\def\ghi

// Erases '\\' as a escape mark.
console.log(format({}, 'C:\\\\abc\\\\def\\\\ghi'));
// => console.log('C:\\abc\\def\\ghi') => C:\abc\def\ghi

// Not erases '\\' in arguments.
console.log(format({}, '{1}', 'C:\\abc\\def\\ghi'));
// => console.log('C:\\abc\\def\\ghi') => C:\abc\def\ghi

// format() and next log() erase double '\\' as escape marks
log(format({}, 'C:\\\\\\\\abc\\\\\\\\def\\\\\\\\ghi'));
// => log('C:\\\\abc\\\\def\\\\ghi') => C:\abc\def\ghi

// Only log() erases '\\' as a escape mark.
log(format({}, '{1}', 'C:\\\\abc\\\\def\\\\ghi'));
// => log('C:\\\\abc\\\\def\\\\ghi') => C:\abc\def\ghi

// Neither log() nor format() erase '\\'
log('{1}', format({}, '{1}', 'C:\\abc\\def\\ghi'));
// => log('{1]", 'C:\\abc\\def\\ghi') => C:\abc\def\ghi

Style block for argument

A logging function can take multiple arguments. A style block to be converted to an argument is same format with a normal style block but its style name is a number starting from 1, which indicates the index of the argument, like {2} or {2: Explanatory text }. A block content in a style block for an argument is never used, so it can be used as an explanatory text.

• { 1 } → replaced with the second argument (the first argument except the template text) of logging function, or an empty string if the second argument is not given.
• { 3 : yyyy } → replaced with the fourth argument (the third argument except the template text) of logging function, or an empty string if the fourth argument is not given. ('yyyy' is never used.)

themingLog.format(theme, template [, ...args]) : string

Parses template text and converts it to a decorated string with theme and args.

Parameters:

| Parameter | Type | Description | | :--------- | :----: | :------------------------------------------------------------------------------------ | | theme | object | An object which is a map of style names and either style functions or template texts. | | template | string | A template text (explained above) | | args | any | Style blocks for arguments (explained above) |

Returns:

A converted string.

themingLog.formatLines(theme, template [, ...args]) : Array

Parses template text, converts it to a decorated string with theme and args, and splits the decorated string to multiple lines with newline codes.

Parameters:

| Parameter | Type | Description | | :--------- | :----: | :------------------------------------------------------------------------------------ | | theme | object | An object which is a map of style names and either style functions or template texts. | | template | string | A template text (explained above) | | args | any | Style blocks for arguments (explained above) |

Returns:

An array of converted string splitted by newline codes.

License

MIT