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();