NativeScript StringFormat

A NativeScript module for handling strings.

NativeScript Toolbox

This module is part of nativescript-toolbox.

License

MIT license

Platforms

Android
iOS

Installation

Run

tns plugin add nativescript-stringformat

inside your app project to install the module.

Demo

For quick start have a look at the demo/app/main-view-model.js file of the demo app to learn how it works.

Otherwise ...

Documentation

The full documentation can be found on readme.io.

Examples

Simple example

import StringFormat = require('nativescript-stringformat');

// "TM + MK"
var newStr1 = StringFormat.format("{0} + {1}",
                                  "TM",  // {0}
                                  "MK");  // {1}
                                 
// the alternative:
var newStr2 = StringFormat.formatArray("{0} + {1}",
                                       ["TM", "MK"]);

Custom order of arguments

import StringFormat = require('nativescript-stringformat');

// "Marcel Kloubert"
var newStr = StringFormat.format("{1} {0}",
                                 "Kloubert",   // {0}
                                 "Marcel");  // {1}

Functions as arguments

You can use functions that return the value that should be included into the target string:

import StringFormat = require('nativescript-stringformat');

// "23091979 + 5091979 = 28183958"
var newStr = StringFormat.format("{0} + {1} = {2}",
                                 23091979,  // {0}
                                 5091979,  // {1}
                                 function (index, args) {  // {2}
                                     return args[0] + args[1];  // 28183958
                                 });

The full signature of a function:

function (index, args, match, formatExpr, funcDepth) {
    return <THE-VALUE-TO-USE>;
}

Name	Description
index	The index value of the argument. For `{7}` this will be `7`
args	The values that were passed to the underlying `format()` or `formatArray()` function.
match	The complete (unhandled) expression of the argument.
formatExpr	The optional format expression of the argument. For `{0:lower}` this will be `lower`.
funcDepth	This value is `0` at the beginning. If you return a function in that function again, this will increase until you stop to return a function.

Format providers

Separated by a : an argument can contain a format expression at the right side.

So you can define custom logic to convert an argument value.

Lets say we want to define a format provider that converts values to upper and lower case strings:

import StringFormat = require("nativescript-stringformat");

StringFormat.addFormatProvider(function(ctx) {    
    var toStringSafe = function() { 
        return ctx.value ? ctx.value.toString() : "";
    }
    
    if (ctx.expression === "upper") {
        // UPPER case
        ctx.handled = true;
        return toStringSafe().toUpperCase();
    }
    
    if (ctx.expression === "lower") {
        // LOWER case
        ctx.handled = true;
        return toStringSafe().toLowerCase();
    }
});

Now you can use the extended logic in your code:

import StringFormat = require('nativescript-stringformat');

// MARCEL kloubert
var newStr = StringFormat.format("{0:upper} {1:lower}",
                                 "Marcel", "KlOUBERT");

The ctx object of a provider callback has the following structure:

Name	Description
expression	The expression right to `:`. In that example `upper` and `lower`.
handled	Defines if value was handled or not. Is `(false)` by default.
value	The value that should be parsed. In that example `Marcel` and `KlOUBERT`.

The parsed value has to be returned and ctx.handled has to be set to (true).

All upcoming format providers will be skipped if the value has been marked as "handled".

Helper functions and classes

Functions

Name	Description
compare	Compares two strings.
concat	Joins elements of an array to one string.
isEmpty	Checks if a string is undefined, (null) or empty.
isEmptyOrWhitespace	Checks if a string is undefined, (null), empty or contains whitespaces only.
isNullOrEmpty	Checks if a string is (null) or empty.
isNullOrUndefined	Checks if a string is (null) or undefined.
isNullOrWhitespace	Checks if a string is (null), empty or contains whitespaces only.
isWhitespace	Checks if a string is empty or contains whitespaces only.
join	Joins elements of an array to one string by using a separator.
similarity	Calculates the similarity between two strings.

Classes

StringBuilder

import StringFormat = require('nativescript-stringformat');

var builder = new StringFormat.StringBuilder();

for (var i = 0; i < 5; i++) {
    builder.appendFormat("Line #{1}: {0}", i, i + 1)
           .appendLine();
}

// "Line 1: 0
// Line 2: 1
// Line 3: 2
// Line 4: 3
// Line 5: 4"
var str = builder.toString();