msub

Adds a simple, localization-friendly "msub" string replacement method to String class, including support for date values.

Declares typescript types.

Install via NPM

npm install msub

Include in your project

Adds an msub method to the String class. This only needs to be included in your project once.

require('msub');

This package also creates an msub singleton. When needing to access this singleton (e.g. to call init method):

// Access msub singleton
var msub = require('msub').msub;

With typescript, retrieves msub singleton with it's init method.

import { msub } from 'msub';

Default Use

The msub method replaces all instances of a ${prop} in a string with a value. Substitutions may be specified as property key/value pairs in an object, or as array entries.

var newString = 'This ${a} ${bC} string'.msub({ bC: 'my', a: 'is' });
var newString = 'This ${1} {$0} string'.msub('my', 'is');
var newString = 'This ${1} ${0} string'.msub(['my', 'is']);

Arguments

Accepts three forms of arguments:

• Object: Key, value pair where all instances of ${key} are replaced with value (see Values section below). In the special case where the key contains a colon, a formatter will be called. For example
  • ${a:YYYYMMDD} will use the format callback if specified
  • ${a:getFullYear} will use Date's getFullYear method (tests if a Date and method exists on Date).
  • ${a:toFixed:2} will use Number's toFixed(2) method (tests if a number and method exists on number).
• A list of argument values (treated as an array)
• An array: replaces ${0}, ${1}, ${2}, etc. with first, second, third, etc argument value.

The first variation of the method is useful for printing out properties of an object.

var myObj = {
  id: 123,
  cn: 'My common name',
  transId: '446'
};
console.log('Processing object ${id}, ${cn} for ${transId}'.msub(myObj));

If you need to use the actual string ${0} in your string, use the object variant of the method, for example:

var obj = { s: 'instance' };
console.log('This ${s} of ${0} actually belongs in the string'.msub(obj));

This instance of ${0} actually belongs in the string

Values

Values can be strings, numbers, booleans or, dates.

If the corresponding key in the string does not contain a colon, the values are directly converted to Strings.

If the key contains a colon then formatting may occur. msub first looks at the value type (must be date or number) and to see if the format string is a compatible name of a method on a Date or Number. If it is then that method will be called. Otherwise, if a format callback is provided, that callback will be called with the value and format string. See Formatting below for more information.

Initialization Options

• open (string) - Specify an open string delimiter, for example use { to use {myString} rather than ${myString}. Defaults to ${.
• close (string) - Specify a close string delimiter. Usually the closing brace will be automatically selected to match the opening brace (see supported matching braces below). Defaults to }.
• uppercase (boolean) - If true, uppercase property names within the string are converted to camelcase before referencing values in the msub parameter dictionary (e.g. MY_STRING becomes myString).
• format (function) - Callback, if specified, to use to format values that contain a colon. Called with the value and the optional portion of the substitution that is after the colon (see Formatting below).

Supported matching braces:

'${': '}',
'#{': '}',
'{{': '}}',
'{': '}',
'(': ')',
'[': ']',
'<': '>',
'<<': '>>'

To use string delimiter

require('msub')({ open: '{' });
var newString = 'This {a} {bC} string'.msub({ bC: 'my', a: 'is' });

To support uppercase property names of form {MY_STRING} that are converted to camelcase (MY_STRING becomes myString).

require('msub')({ uppercase: true });
var newString = 'This ${A} ${B_C} string'.msub({ bC: 'my', a: 'is' });

Formatting

msub supports custom formatting of numbers and Date objects via

• the format callback option, set using the init method.
• method names and parameters specified as part of the substitution key (e.g. ${n:toFixed:2}).
  • the method name must exist on the value, otherwise the format callback will be used if it exists.

Example using the moment package.

var moment = require('moment');

require('../dist').msub.init({
  format: function(value, format) {
    if (format && value instanceof Date) {
      return moment(value).format(format);
    }
    return value;
  }
});

var newString = 'Today ${a:YYYYMMDD} and the year ${b:getFullYear} and ${c:} were the best ${d:toFixed:2}'.msub(
  { a: new Date(), b: new Date(1999, 12), c: undefined, d: 43.2345 }
);
console.log(newString);

outputs:

Today 20190808 and the year 2000 and ${c:} were the best 43.23

Versions

Version 3

• Zero external dependencies (previously might have imported moment library)
• Specifies types for typescript
• Changes to init method options:
  • Removes moment and the optional import of moment.js library and passes responsibility for date formatting to the caller.
  • Adds format callback option that can be used for any value, just add a colon and optional format string.
  • Adds close option
  • Closing brace defaults to mirror of open option if open is one of {, [, < or (.

If you are not using moment then you should be safe to upgrade. If you are using moment, you will need to add a format callback option.

Version 2

Version 2 default string replacement specifiers are similar to ES6 string literals, using the syntax ${myVariableName}. Version 2 default behaviour breaks the default version 0.x behaviour.

Initialize msub to use v0.x.x default behaviour as following:

require('msub')({ open: '{', moment: true, uppercase: true });

var newString = 'This {A} {B_C} string'.msub({ bC: 'my', a: 'is' });

Tests

To run the test suite, first install the dependencies, then run npm test:

$ npm install
$ npm test

License

MIT