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function func_get_arg (num) {
    // Get the $arg_num'th argument that was passed to the function  
    // 
    // version: 1008.1718
    // discuss at: http://phpjs.org/functions/func_get_arg    // +   original by: Brett Zamir (http://brett-zamir.me)
    // %        note 1: May not work in all JS implementations
    // *     example 1: function tmp_a() {return func_get_arg(1);}
    // *     example 1: tmp_a('a', 'b');
    // *     returns 1: 'a'    if (!arguments.callee.caller) {
        try {
            throw new Error('Either you are using this in a browser which does not support the "caller" property or you are calling this from a global context');
            //return false;
        } catch (e){            return false;
        }
    }
 
    if (num > arguments.callee.caller.arguments.length - 1) {        try {
            throw new Error('Argument number is greater than the number of arguments actually passed');
            //return false;
        } catch (e2){
            return false;        }
    }
 
    return arguments.callee.caller.arguments[num];
}

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function tmp_a() {return func_get_arg(1);}
tmp_a('a', 'b');

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'a'