Expression parser

Introduction¶

Parse expression string into function.
Parser is generated from jison

Author: Rex
Member of scene

Live demos¶

Usage¶

Sample code

Install plugin¶

Load minify file¶

Load plugin (minify file) in preload stage

scene.load.plugin('rexexpressionparserplugin', 'https://raw.githubusercontent.com/rexrainbow/phaser3-rex-notes/master/dist/rexexpressionparserplugin.min.js', true);

Add parser

var parser = scene.plugins.get('rexexpressionparserplugin').add();

Or, parse expression to function object.

var f = scene.plugins.get('rexexpressionparserplugin').compile(expressionString);
// var value = f(context);

Import plugin¶

Install rex plugins from npm
```
npm i phaser3-rex-plugins
```

Install plugin in configuration of game

import ExpressionParserPlugin from 'phaser3-rex-plugins/plugins/expressionparser-plugin.js';
var config = {
    // ...
    plugins: {
        global: [{
            key: 'rexExpressionParserPlugin',
            plugin: ExpressionParserPlugin,
            start: true
        },
        // ...
        ]
    }
    // ...
};
var game = new Phaser.Game(config);

Add parser

var parser = scene.plugins.get('rexExpressionParserPlugin').add();

Or, parse expression to function object.

var f = scene.plugins.get('rexExpressionParserPlugin').compile(expressionString);
// var value = f(context);

Import class¶

Install rex plugins from npm
```
npm i phaser3-rex-plugins
```

Import class

import ExpressionParser from 'phaser3-rex-plugins/plugins/expressionparser.js';

Add parser
```
var parser = new ExpressionParser();
```

Create instance¶

var parser = scene.plugins.get('rexExpressionParserPlugin').add();

Execute¶

Compile then execute¶

Compile expression string into function
```
var f = parser.compile(expressionString);
```
or
```
var f = scene.plugins.get('rexExpressionParserPlugin').compile(expressionString);
```
- expressionString :
  - Number : 1, 1.5, 0xf.
  - Variable : a, $a, _a, a.$b._c_, a['b'].c
  - Arithmetic : +, -, *, \, %, (, ), ex : '(a + b.c) * 3 + (2 % 3)'.
  - Boolean : >, <, >=, <=, ==, !=, &&, ||, ex '(a > 10) && (a < 30) || (b.c > c)'.
  - Condition : (cond)? v0:v1, ex'(a > b.c)? a:b.c'.
  - Custom method : randomInt(a, b.c).
  - String concat : 'Hello ' + name.

Invoke function

var value = f(context);

f : Function object from compiled result.

context : Varables used in expression.

{
    a: 10,  // Number
    b: {c: 10},  // Objet with number property
    c: 20,
    randomInt(a, b) {  // Custom method
        return Math.floor(Math.random()*(b-a)+a);
    }
}

Execute directly¶

var value = parser.exec(expressionString, context);

or

var value = parser.exec(f, context);

Custom method¶

Add method into parser instance

var parser = scene.plugins.get('rexExpressionParserPlugin').add();
parser.randomInt = function(a, b) {
    return Math.floor(Math.random()*(b-a)+a); 
}
// var value = parser.exec('randomInt(a, b)', {a:10, b:20});

Declare method into class of parser

class MyParser extends ExpressionParser {
    randomInt(a, b) {
        return Math.floor(Math.random()*(b-a)+a); 
    }
}
var parser = new MyParser();
// var value = parser.exec('randomInt(a, b)', {a:10, b:20});

Add method into context

var context = {
    a: 10,
    b: 20,
    randomInt(a, b) {  // Custom method
        return Math.floor(Math.random()*(b-a)+a);
    }
}
var value = parser.exec('randomInt(a, b)', context);

Proxy as context¶

Proxy with has and get handlers could be a context.

For example, proxy scene data :

var context = new Proxy({}, {
    has(target, key) {
        return scene.data.has(key);
    },
    get(target, prop) {
        return scene.data.get(prop);
    }
})

or

var context = scene.plugins.get('rexExpressionParserPlugin').createProxyContext({
    has(target, key) {
        // return boolean
    },
    get(target, prop) {
        // return any;
    }
})