A Ruby-like "range" for JavaScript

rb-range.js

// A Ruby-like "range" for JavaScript
// https://github.com/thunder9 
// 
// Require: https://github.com/thunder9/rb-enumerable.js

(function (global) {
    
    if (!global.RubyLike.enumerable || !global.RubyLike.Enumerator) {
        throw Error('rb-enumerable.js required');
    }
    var rl = global.RubyLike;

    var Range = function (first, last, exclude_end) {
        if (!(this instanceof Range)) {
            return new Range(first, last, exclude_end);
        }
        var enm = rl.Enumerator();
        if (isnum(first) && isnum(last)) {
            var source;
            if (exclude_end) {
                source = function (yielder) {
                    for (var val = first; val < last; val++) {
                        yielder(val);
                    }
                };             
            } else {
                source = function (yielder) {
                    for (var val = first; val <= last; val++) {
                        yielder(val);
                    }
                };                       
            }
            enm = rl.Enumerator(source);
        }
        if (isfunc(first.succ) && isfunc(first.spaceship)) {
            var n = exclude_end ? -1 : 0;
            enm = rl.Enumerator(function (yielder) {
                for (var val = first; val.spaceship(last) <= n; val = val.succ()) {
                    yielder(val);
                }
            });                
        }
        this.each = function (yielder) {           
            if (isfunc(yielder)) {
                enm.each(function (val) { yielder(val); });
                return this;
            } else {
                return enm;
            }
        };
        var getters = {
            first: { get: function () { return first; } },
            last: { get: function () { return last; } },
            exclude_end: { get: function () { return exclude_end; } }
        };
        if (isfunc(Object.defineProperties)) {
            Object.defineProperties(this, getters);
        } else {
            this.get_first = getters.first.get
            this.get_last = getters.last.get
            this.get_exclude_end = getters.exclude_end.get
        }
    };

    var RangeProto = function () {
        this.cover = function (obj) {
            var r = get_param(this);
            if (isnum(obj) && isnum(r.first) && isnum(r.last)) {
                if (r.exclude_end) {
                    return obj >= r.first && obj < r.last;
                } else {
                    return obj >= r.first && obj <= r.last;
                }
            }
            if (isfunc(obj.spaceship)) {
                return obj.spaceship(r.first) === 1
                    && obj.spaceship(r.last) <= (r.exclude_end ? -1 : 0);
            }
            return false;   
        };
        this.member = function (obj) {
            var r = get_param(this);
            if (isnum(r.first) && isnum(r.last)) {
                return this.cover(obj);
            } else {
                return rl.enumerable.member.call(this, obj);
            }
            return false
        },
        this.include = this.member;
        this.step = function (s, block) {
            if (!isnum(s)) { s = 1; }
            var counted = 0;
            var enm = rl.Enumerator(this, function (yielder, val) {
                if (counted++ % s === 0) {
                    yielder(val);
                }
            }); 
            if (isfunc(block)) {
                enm.each(function (val) { block(val); });
                return this;
            } else {
                return enm;
            }            
        };
        this.eql = function (other) {
            var r = get_param(this);
            var o = get_param(other);
            if (other instanceof Range && r.exclude_end === o.exclude_end) {
                if (isnum(r.first) && isnum(r.last)
                    && isnum(o.first) && isnum(o.last)) {
                    return r.first === o.first && r.last === o.last;    
                } else if (isfunc(r.first.eql) && isfunc(r.last.eql)) {
                    return r.first.eql(o.first) && r.last.eql(o.last);
                }
            }
            return false;
        };
        this.begin = this.first;
        this.end = this.last;
    }

    var classof = function (obj) {
        if (obj === null) return 'Null';
        if (obj === undefined) return 'Undefined';
        return Object.prototype.toString.call(obj).slice(8, -1);
    };
    var isnum = function (obj) {
        return classof(obj) === 'Number';
    };
    var isfunc = function (obj) {
        return classof(obj) === 'Function';
    }
        
    var get_param = function (range) {
        if (isfunc(Object.defineProperties)) {
            return range;
        } else {
            return {
                first: range.get_first(),
                last: range.get_last(),
                exclude_end: range.get_exclude_end()
            };
        }
    };
  
    RangeProto.prototype = rl.enumerable;
    Range.prototype = new RangeProto();
        
    rl.Range = Range;
    
} (this));

test.html

<!DOCTYPE html>
<html>
<head>
<script src="https://raw.github.com/thunder9/rb-enumerable.js/master/rb-enumerable.js"></script>
<script src="rb-range.js"></script>
</head>
<body>
<pre id="out"></pre>
<script>

var p = function (o) {
    var out = document.getElementById('out');
    p = function (o) {
        out.innerHTML += '// ' + JSON.stringify(o);
        out.appendChild(document.createElement('br'));
    }
    p(o);
};

var rl = RubyLike;

if (typeof Object.defineProperties === 'function') {
    rl.iteration_limit = 1000; //ES5
} else {
    rl.set_iteration_limit(1000);
}

p(rl.Range(-5,10).map(function (x) { return x*2; }).to_a());
p(rl.Range(-5,10,true).map(function (x) { return x*2; }).to_a());

var Int = function (val) {
    if (!(this instanceof Int)) {
        return new Int(val);
    }
    this.val = val;
    this.succ = function () { return Int(this.val + 1); };
    this.spaceship = function (other) {
        if (this.val === other.val) { return 0; }
        else if (this.val > other.val) { return 1; }
        else { return -1; }                    
    };
    this.eql = function (other) {
        return this.spaceship(other) === 0;        
    }
};

p(rl.Range(Int(-5),Int(10)).map(function (x) { return x.val*2; }).to_a());
p(rl.Range(Int(-5),Int(10),true).map(function (x) { return x.val*2; }).to_a());

p(rl.Range(-5,10).step(3).to_a());
p(rl.Range(-5,10,true).step(3).to_a());

p(rl.Range(-5,10).cover(6));
p(rl.Range(-5,10).cover(-5000));
p(rl.Range(Int(-5),Int(10)).cover(Int(6)));
p(rl.Range(Int(-5),Int(10)).cover(Int(6.5)));
p(rl.Range(Int(-5),Int(10)).cover(Int(-5000)));

p(rl.Range(Int(-5),Int(10)).member(Int(6)));
p(rl.Range(Int(-5),Int(10)).member(Int(6.5)));
        
p(rl.Range(-5,10).eql(rl.Range(-5,10)));
p(rl.Range(-5,10).eql(rl.Range(-5,11)));
p(rl.Range(Int(-5),Int(10)).eql(rl.Range(Int(-5),Int(10))));
p(rl.Range(Int(-5),Int(10)).eql(rl.Range(Int(-5),Int(11))));

</script>
</body>
</html>