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first underscore.js commit -- pulled out from documentcloud's core.js
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jashkenas committed Oct 25, 2009
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// Javascript can be so much more pleasant when it's functional -- re-implement
// a bunch of utility methods from Prototype and Steele's Functional...
window._ = {

// The cornerstone, an each implementation.
// Handles objects implementing forEach, _each, arrays, and raw objects.
each : function(obj, iterator, context) {
var index = 0;
try {
if (obj.forEach) {
obj.forEach(iterator, context);
} else if (obj.length) {
for (var i=0; i<obj.length; i++) {
iterator.call(context, obj[i], i);
}
} else if (obj._each) {
obj._each(function(value) {
iterator.call(context, value, index++);
});
} else {
var i = 0;
for (var key in obj) {
var value = obj[key], pair = [key, value];
pair.key = key;
pair.value = value;
iterator.call(context, pair, i++);
}
}
} catch(e) {
if (e != '__break__') throw e;
}
return obj;
},

// Determine whether all of the elements match a truth test. Delegate to
// Javascript 1.6's every(), if it is present.
all : function(obj, iterator, context) {
if (obj.every) return obj.every(iterator, context);
var result = true;
_.each(obj, function(value, index) {
result = result && !!iterator.call(context, value, index);
if (!result) throw '__break__';
});
return result;
},

// Determine if at least one element in the object matches a truth test. Use
// Javascript 1.6's some(), if it exists.
any : function(obj, iterator, context) {
if (obj.some) return obj.some(iterator, context);
var result = false;
_.each(obj, function(value, index) {
if (result = !!iterator.call(context, value, index)) throw '__break__';
});
return result;
},

// Return the results of applying the iterator to each element. Use Javascript
// 1.6's version of map, if possible.
map : function(obj, iterator, context) {
if (obj.map) return obj.map(iterator, context);
var results = [];
_.each(obj, function(value, index) {
results.push(iterator.call(context, value, index));
});
return results;
},

// Return the first value which passes a truth test.
detect : function(obj, iterator, context) {
var result;
_.each(obj, function(value, index) {
if (iterator.call(context, value, index)) {
result = value;
throw '__break__';
}
});
return result;
},

// Return all the elements that pass a truth test. Use Javascript 1.6's
// filter(), if it exists.
select : function(obj, iterator, context) {
if (obj.filter) return obj.filter(iterator, context);
var results = [];
_.each(obj, function(value, index) {
if (iterator.call(context, value, index)) results.push(value);
});
return results;
},

// Determine if a given value is included in the object, based on '=='.
include : function(obj, target) {
if (_.isArray(obj)) if (obj.indexOf(target) != -1) return true;
var found = false;
_.each(obj, function(value) {
if (value == target) {
found = true;
throw '__break__';
}
});
return found;
},

// Aka reduce. Inject builds up a single result from a list of values.
inject : function(obj, memo, iterator, context) {
_.each(obj, function(value, index) {
memo = iterator.call(context, memo, value, index);
});
return memo;
},

// Invoke a method with arguments on every item in a collection.
invoke : function(obj, method) {
var args = _.toArray(arguments).slice(2);
return _.map(obj, function(value) {
return (method ? value[method] : value).apply(value, args);
});
},

// Return the maximum item or (item-based computation).
max : function(obj, iterator, context) {
var result;
_.each(obj, function(value, index) {
value = iterator ? iterator.call(context, value, index) : value;
if (result == null || value >= result) result = value;
});
return result;
},

// Return the minimum element (or element-based computation).
min : function(obj, iterator, context) {
var result;
_.each(obj, function(value, index) {
value = iterator ? iterator.call(context, value, index) : value;
if (result == null || value < result) result = value;
});
return result;
},

// Optimized version of a common use case of map: fetching a property.
pluck : function(obj, key) {
var results = [];
_.each(obj, function(value){ results.push(value[key]); });
return results;
},

// Return all the elements for which a truth test fails.
reject : function(obj, iterator, context) {
var results = [];
_.each(obj, function(value, index) {
if (!iterator.call(context, value, index)) results.push(value);
});
return results;
},

// Sort the object's values by a criteria produced by an iterator.
sortBy : function(obj, iterator, context) {
return _.pluck(_.map(obj, function(value, index) {
return {
value : value,
criteria : iterator.call(context, value, index)
};
}).sort(function(left, right) {
var a = left.criteria, b = right.criteria;
return a < b ? -1 : a > b ? 1 : 0;
}), 'value');
},

// Use a comparator function to figure out at what index an object should
// be inserted so as to maintain order. Uses binary search.
sortedIndex : function(array, comparator, obj) {
var low = 0, high = array.length;
while (low < high) {
var mid = (low + high) >> 1;
comparator(array[mid], obj) < 0 ? low = mid + 1 : high = mid;
}
return low;
},

// Convert anything iterable into a real, live array.
toArray : function(iterable) {
if (!iterable) return [];
if (_.isArray(iterable)) return iterable;
return _.map(iterable, function(val){ return val; });
},

// Return the number of elements in an object.
size : function(obj) {
_.toArray(obj).length;
},

//------------- The following methods only apply to arrays. -----------------

// Get the first element of an array.
first : function(array) {
return array[0];
},

// Get the last element of an array.
last : function(array) {
return array[array.length - 1];
},

// Trim out all falsy values from an array.
compact : function(array) {
return _.select(array, function(value){ return !!value; });
},

// Return a completely flattened version of an array.
flatten : function(array) {
return _.inject(array, [], function(memo, value) {
if (_.isArray(value)) return memo.concat(_.flatten(value));
memo.push(value);
return memo;
});
},

// Return a version of the array that does not contain the specified value.
without : function(array) {
var values = array.slice.call(arguments, 0);
return _.select(function(value){ return !_.include(values, value); });
},

// Produce a duplicate-free version of the array. If the array has already
// been sorted, you have the option of using a faster algorithm.
uniq : function(array, sorted) {
return _.inject(array, [], function(memo, el, i) {
if (0 == i || (sorted ? _.last(memo) != el : !_.include(memo, el))) memo.push(el);
return memo;
});
},

// Produce an array that contains every item shared between two given arrays.
intersect : function(array1, array2) {
return _.select(_.uniq(array1), function(item1) {
return _.detect(array2, function(item2) { return item1 === item2; });
});
},

// If the browser doesn't supply us with indexOf, we might need this function.
// Return the position of the first occurence of an item in an array,
// or -1 if the item is not included in the array.
// indexOf : function(array, item) {
// var length = array.length;
// for (i=0; i<length; i++) if (array[i] === item) return i;
// return -1;
// }

/* ---------------- The following methods apply to objects ---------------- */

// Retrieve the names of an object's properties.
keys : function(obj) {
return _.pluck(obj, 'key');
},

// Retrieve the values of an object's properties.
values : function(obj) {
return _.pluck(obj, 'value');
},

// Extend a given object with all of the properties in a source object.
extend : function(destination, source) {
for (var property in source) destination[property] = source[property];
return destination;
},

// Create a (shallow-cloned) duplicate of an object.
clone : function(obj) {
return _.extend({}, obj);
},

// Is a given value a DOM element?
isElement : function(obj) {
return !!(obj && obj.nodeType == 1);
},

// Is a given value a real Array?
isArray : function(obj) {
return Object.prototype.toString.call(obj) == '[object Array]';
},

// Is a given value a Function?
isFunction : function(obj) {
return typeof obj == 'function';
},

// Is a given variable undefined?
isUndefined : function(obj) {
return typeof obj == 'undefined';
},

// Convert any value into printable string form.
toString : function(obj) {
return obj == null ? '' : String(obj);
},

// Create a function bound to a given object (assigning 'this', and arguments,
// optionally).
bind : function(func, context) {
if (!context) return func;
var args = _.toArray(arguments).slice(2);
return function() {
var a = args.concat(_.toArray(arguments));
return func.apply(context, a);
};
},

// Bind all of an object's methods to that object. Useful for ensuring that
// all callbacks defined on an object belong to it.
bindAll : function() {
var args = _.toArray(arguments);
var context = args.pop();
_.each(args, function(methodName) {
context[methodName] = _.bind(context[methodName], context);
});
},

// Generate a unique integer id (unique within the entire client session).
// Useful for temporary DOM ids.
uniqueId : function(prefix) {
var id = this._idCounter = (this._idCounter || 0) + 1;
return prefix ? prefix + id : id;
},

// Perform a deep comparison to check if two objects are equal.
isEqual : function(a, b) {
// Check object identity.
if (a === b) return true;
// Different types?
var at = typeof(a), bt = typeof(b);
if (at != bt) return false;
// Basic equality test (watch out for coercions).
if (a == b) return true;
// One of them implements an isEqual()?
if (a.isEqual) return a.isEqual(b);
// Nothing else worked, deep compare the contents.
return at === 'object' && _.isEqualContents(a, b);
},

// Objects have equal contents if they have the same keys, and all the values
// are equal (as defined by _.isEqual).
_isEqualContents : function(a, b) {
var aKeys = _.keys(a), bKeys = _.keys(b);
if (aKeys.length != bKeys.length) return false;
for (var key in a) if (!_.isEqual(a[key], b[key])) return false;
return true;
},

// Javascript templating a-la ERB, pilfered from John Resig's
// "Secrets of the Javascript Ninja", page 83.
template : function(str, data) {
var fn = new Function('obj',
'var p=[],print=function(){p.push.apply(p,arguments);};' +
'with(obj){p.push(\'' +
str
.replace(/[\r\t\n]/g, " ")
.split("<%").join("\t")
.replace(/((^|%>)[^\t]*)'/g, "$1\r")
.replace(/\t=(.*?)%>/g, "',$1,'")
.split("\t").join("');")
.split("%>").join("p.push('")
.split("\r").join("\\'")
+ "');}return p.join('');");
return data ? fn(data) : fn;
}

};

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