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function is_callable (v, syntax_only, callable_name) {
    // Returns true if var is callable.  
    // 
    // version: 1109.2015
    // discuss at: http://phpjs.org/functions/is_callable    // +   original by: Brett Zamir (http://brett-zamir.me)
    // %        note 1: The variable callable_name cannot work as a string variable passed by reference as in PHP (since JavaScript does not support passing strings by reference), but instead will take the name of a global variable and set that instead
    // %        note 2: When used on an object, depends on a constructor property being kept on the object prototype
    // *     example 1: is_callable('is_callable');
    // *     returns 1: true    // *     example 2: is_callable('bogusFunction', true);
    // *     returns 2:true // gives true because does not do strict checking
    // *     example 3: function SomeClass () {}
    // *     example 3: SomeClass.prototype.someMethod = function (){};
    // *     example 3: var testObj = new SomeClass();    // *     example 3: is_callable([testObj, 'someMethod'], true, 'myVar');
    // *     example 3: alert(myVar); // 'SomeClass::someMethod'
    var name = '',
        obj = {},
        method = '';    var getFuncName = function (fn) {
        var name = (/\W*function\s+([\w\$]+)\s*\(/).exec(fn);
        if (!name) {
            return '(Anonymous)';
        }        return name[1];
    };
    if (typeof v === 'string') {
        obj = this.window;
        method = v;        name = v;
    }
    else if (Object.prototype.toString.call(v) === '[object Array]' && 
                v.length === 2 && typeof v[0] === 'object' && typeof v[1] === 'string') {
        obj = v[0];        method = v[1];
        name = (obj.constructor && getFuncName(obj.constructor)) + '::' + method;
    }
    else {
        return false;    }
    if (syntax_only || typeof obj[method] === 'function') {
        if (callable_name) {
            this.window[callable_name] = name;
        }        return true;
    }
    return false;
}

1

is_callable('is_callable');

1

true

1

is_callable('bogusFunction', true);

1

true // gives true because does not do strict checking