@ramda/countby
Version:
R.countBy exported as a module
519 lines (486 loc) • 17.3 kB
JavaScript
// Ramda v0.26.1
// https://github.com/ramda/ramda
// (c) 2013-2019 Scott Sauyet, Michael Hurley, and David Chambers
// Ramda may be freely distributed under the MIT license.
(function (global, factory) {
typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
typeof define === 'function' && define.amd ? define(['exports'], factory) :
(factory((global.R = {})));
}(this, (function (exports) { 'use strict';
function _cloneRegExp(pattern) {
return new RegExp(pattern.source, (pattern.global ? 'g' : '') +
(pattern.ignoreCase ? 'i' : '') +
(pattern.multiline ? 'm' : '') +
(pattern.sticky ? 'y' : '') +
(pattern.unicode ? 'u' : ''));
}
function _isPlaceholder(a) {
return a != null &&
typeof a === 'object' &&
a['@@functional/placeholder'] === true;
}
/**
* Optimized internal one-arity curry function.
*
* @private
* @category Function
* @param {Function} fn The function to curry.
* @return {Function} The curried function.
*/
function _curry1(fn) {
return function f1(a) {
if (arguments.length === 0 || _isPlaceholder(a)) {
return f1;
} else {
return fn.apply(this, arguments);
}
};
}
/**
* Gives a single-word string description of the (native) type of a value,
* returning such answers as 'Object', 'Number', 'Array', or 'Null'. Does not
* attempt to distinguish user Object types any further, reporting them all as
* 'Object'.
*
* @func
* @memberOf R
* @since v0.8.0
* @category Type
* @sig (* -> {*}) -> String
* @param {*} val The value to test
* @return {String}
* @example
*
* R.type({}); //=> "Object"
* R.type(1); //=> "Number"
* R.type(false); //=> "Boolean"
* R.type('s'); //=> "String"
* R.type(null); //=> "Null"
* R.type([]); //=> "Array"
* R.type(/[A-z]/); //=> "RegExp"
* R.type(() => {}); //=> "Function"
* R.type(undefined); //=> "Undefined"
*/
var type = _curry1(function type(val) {
return val === null
? 'Null'
: val === undefined
? 'Undefined'
: Object.prototype.toString.call(val).slice(8, -1);
});
/**
* Copies an object.
*
* @private
* @param {*} value The value to be copied
* @param {Array} refFrom Array containing the source references
* @param {Array} refTo Array containing the copied source references
* @param {Boolean} deep Whether or not to perform deep cloning.
* @return {*} The copied value.
*/
function _clone(value, refFrom, refTo, deep) {
var copy = function copy(copiedValue) {
var len = refFrom.length;
var idx = 0;
while (idx < len) {
if (value === refFrom[idx]) {
return refTo[idx];
}
idx += 1;
}
refFrom[idx + 1] = value;
refTo[idx + 1] = copiedValue;
for (var key in value) {
copiedValue[key] = deep ?
_clone(value[key], refFrom, refTo, true) : value[key];
}
return copiedValue;
};
switch (type(value)) {
case 'Object': return copy({});
case 'Array': return copy([]);
case 'Date': return new Date(value.valueOf());
case 'RegExp': return _cloneRegExp(value);
default: return value;
}
}
function _arity(n, fn) {
/* eslint-disable no-unused-vars */
switch (n) {
case 0: return function() { return fn.apply(this, arguments); };
case 1: return function(a0) { return fn.apply(this, arguments); };
case 2: return function(a0, a1) { return fn.apply(this, arguments); };
case 3: return function(a0, a1, a2) { return fn.apply(this, arguments); };
case 4: return function(a0, a1, a2, a3) { return fn.apply(this, arguments); };
case 5: return function(a0, a1, a2, a3, a4) { return fn.apply(this, arguments); };
case 6: return function(a0, a1, a2, a3, a4, a5) { return fn.apply(this, arguments); };
case 7: return function(a0, a1, a2, a3, a4, a5, a6) { return fn.apply(this, arguments); };
case 8: return function(a0, a1, a2, a3, a4, a5, a6, a7) { return fn.apply(this, arguments); };
case 9: return function(a0, a1, a2, a3, a4, a5, a6, a7, a8) { return fn.apply(this, arguments); };
case 10: return function(a0, a1, a2, a3, a4, a5, a6, a7, a8, a9) { return fn.apply(this, arguments); };
default: throw new Error('First argument to _arity must be a non-negative integer no greater than ten');
}
}
/**
* Internal curryN function.
*
* @private
* @category Function
* @param {Number} length The arity of the curried function.
* @param {Array} received An array of arguments received thus far.
* @param {Function} fn The function to curry.
* @return {Function} The curried function.
*/
function _curryN(length, received, fn) {
return function() {
var combined = [];
var argsIdx = 0;
var left = length;
var combinedIdx = 0;
while (combinedIdx < received.length || argsIdx < arguments.length) {
var result;
if (combinedIdx < received.length &&
(!_isPlaceholder(received[combinedIdx]) ||
argsIdx >= arguments.length)) {
result = received[combinedIdx];
} else {
result = arguments[argsIdx];
argsIdx += 1;
}
combined[combinedIdx] = result;
if (!_isPlaceholder(result)) {
left -= 1;
}
combinedIdx += 1;
}
return left <= 0
? fn.apply(this, combined)
: _arity(left, _curryN(length, combined, fn));
};
}
/**
* Tests whether or not an object is an array.
*
* @private
* @param {*} val The object to test.
* @return {Boolean} `true` if `val` is an array, `false` otherwise.
* @example
*
* _isArray([]); //=> true
* _isArray(null); //=> false
* _isArray({}); //=> false
*/
var _isArray = Array.isArray || function _isArray(val) {
return (val != null &&
val.length >= 0 &&
Object.prototype.toString.call(val) === '[object Array]');
};
function _isTransformer(obj) {
return obj != null && typeof obj['@@transducer/step'] === 'function';
}
/**
* Returns a function that dispatches with different strategies based on the
* object in list position (last argument). If it is an array, executes [fn].
* Otherwise, if it has a function with one of the given method names, it will
* execute that function (functor case). Otherwise, if it is a transformer,
* uses transducer [xf] to return a new transformer (transducer case).
* Otherwise, it will default to executing [fn].
*
* @private
* @param {Array} methodNames properties to check for a custom implementation
* @param {Function} xf transducer to initialize if object is transformer
* @param {Function} fn default ramda implementation
* @return {Function} A function that dispatches on object in list position
*/
function _dispatchable(methodNames, xf, fn) {
return function() {
if (arguments.length === 0) {
return fn();
}
var args = Array.prototype.slice.call(arguments, 0);
var obj = args.pop();
if (!_isArray(obj)) {
var idx = 0;
while (idx < methodNames.length) {
if (typeof obj[methodNames[idx]] === 'function') {
return obj[methodNames[idx]].apply(obj, args);
}
idx += 1;
}
if (_isTransformer(obj)) {
var transducer = xf.apply(null, args);
return transducer(obj);
}
}
return fn.apply(this, arguments);
};
}
function _has(prop, obj) {
return Object.prototype.hasOwnProperty.call(obj, prop);
}
function _isString(x) {
return Object.prototype.toString.call(x) === '[object String]';
}
/**
* Tests whether or not an object is similar to an array.
*
* @private
* @category Type
* @category List
* @sig * -> Boolean
* @param {*} x The object to test.
* @return {Boolean} `true` if `x` has a numeric length property and extreme indices defined; `false` otherwise.
* @example
*
* _isArrayLike([]); //=> true
* _isArrayLike(true); //=> false
* _isArrayLike({}); //=> false
* _isArrayLike({length: 10}); //=> false
* _isArrayLike({0: 'zero', 9: 'nine', length: 10}); //=> true
*/
var _isArrayLike = _curry1(function isArrayLike(x) {
if (_isArray(x)) { return true; }
if (!x) { return false; }
if (typeof x !== 'object') { return false; }
if (_isString(x)) { return false; }
if (x.nodeType === 1) { return !!x.length; }
if (x.length === 0) { return true; }
if (x.length > 0) {
return x.hasOwnProperty(0) && x.hasOwnProperty(x.length - 1);
}
return false;
});
function XWrap(fn) {
this.f = fn;
}
XWrap.prototype['@@transducer/init'] = function() {
throw new Error('init not implemented on XWrap');
};
XWrap.prototype['@@transducer/result'] = function(acc) { return acc; };
XWrap.prototype['@@transducer/step'] = function(acc, x) {
return this.f(acc, x);
};
function _xwrap(fn) { return new XWrap(fn); }
/**
* Optimized internal two-arity curry function.
*
* @private
* @category Function
* @param {Function} fn The function to curry.
* @return {Function} The curried function.
*/
function _curry2(fn) {
return function f2(a, b) {
switch (arguments.length) {
case 0:
return f2;
case 1:
return _isPlaceholder(a)
? f2
: _curry1(function(_b) { return fn(a, _b); });
default:
return _isPlaceholder(a) && _isPlaceholder(b)
? f2
: _isPlaceholder(a)
? _curry1(function(_a) { return fn(_a, b); })
: _isPlaceholder(b)
? _curry1(function(_b) { return fn(a, _b); })
: fn(a, b);
}
};
}
/**
* Creates a function that is bound to a context.
* Note: `R.bind` does not provide the additional argument-binding capabilities of
* [Function.prototype.bind](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind).
*
* @func
* @memberOf R
* @since v0.6.0
* @category Function
* @category Object
* @sig (* -> *) -> {*} -> (* -> *)
* @param {Function} fn The function to bind to context
* @param {Object} thisObj The context to bind `fn` to
* @return {Function} A function that will execute in the context of `thisObj`.
* @see R.partial
* @example
*
* const log = R.bind(console.log, console);
* R.pipe(R.assoc('a', 2), R.tap(log), R.assoc('a', 3))({a: 1}); //=> {a: 3}
* // logs {a: 2}
* @symb R.bind(f, o)(a, b) = f.call(o, a, b)
*/
var bind = _curry2(function bind(fn, thisObj) {
return _arity(fn.length, function() {
return fn.apply(thisObj, arguments);
});
});
function _arrayReduce(xf, acc, list) {
var idx = 0;
var len = list.length;
while (idx < len) {
acc = xf['@@transducer/step'](acc, list[idx]);
if (acc && acc['@@transducer/reduced']) {
acc = acc['@@transducer/value'];
break;
}
idx += 1;
}
return xf['@@transducer/result'](acc);
}
function _iterableReduce(xf, acc, iter) {
var step = iter.next();
while (!step.done) {
acc = xf['@@transducer/step'](acc, step.value);
if (acc && acc['@@transducer/reduced']) {
acc = acc['@@transducer/value'];
break;
}
step = iter.next();
}
return xf['@@transducer/result'](acc);
}
function _methodReduce(xf, acc, obj, methodName) {
return xf['@@transducer/result'](obj[methodName](bind(xf['@@transducer/step'], xf), acc));
}
var symIterator = (typeof Symbol !== 'undefined') ? Symbol.iterator : '@@iterator';
function _reduce(fn, acc, list) {
if (typeof fn === 'function') {
fn = _xwrap(fn);
}
if (_isArrayLike(list)) {
return _arrayReduce(fn, acc, list);
}
if (typeof list['fantasy-land/reduce'] === 'function') {
return _methodReduce(fn, acc, list, 'fantasy-land/reduce');
}
if (list[symIterator] != null) {
return _iterableReduce(fn, acc, list[symIterator]());
}
if (typeof list.next === 'function') {
return _iterableReduce(fn, acc, list);
}
if (typeof list.reduce === 'function') {
return _methodReduce(fn, acc, list, 'reduce');
}
throw new TypeError('reduce: list must be array or iterable');
}
var _xfBase = {
init: function() {
return this.xf['@@transducer/init']();
},
result: function(result) {
return this.xf['@@transducer/result'](result);
}
};
function XReduceBy(valueFn, valueAcc, keyFn, xf) {
this.valueFn = valueFn;
this.valueAcc = valueAcc;
this.keyFn = keyFn;
this.xf = xf;
this.inputs = {};
}
XReduceBy.prototype['@@transducer/init'] = _xfBase.init;
XReduceBy.prototype['@@transducer/result'] = function(result) {
var key;
for (key in this.inputs) {
if (_has(key, this.inputs)) {
result = this.xf['@@transducer/step'](result, this.inputs[key]);
if (result['@@transducer/reduced']) {
result = result['@@transducer/value'];
break;
}
}
}
this.inputs = null;
return this.xf['@@transducer/result'](result);
};
XReduceBy.prototype['@@transducer/step'] = function(result, input) {
var key = this.keyFn(input);
this.inputs[key] = this.inputs[key] || [key, this.valueAcc];
this.inputs[key][1] = this.valueFn(this.inputs[key][1], input);
return result;
};
var _xreduceBy = _curryN(4, [],
function _xreduceBy(valueFn, valueAcc, keyFn, xf) {
return new XReduceBy(valueFn, valueAcc, keyFn, xf);
}
);
/**
* Groups the elements of the list according to the result of calling
* the String-returning function `keyFn` on each element and reduces the elements
* of each group to a single value via the reducer function `valueFn`.
*
* This function is basically a more general [`groupBy`](#groupBy) function.
*
* Acts as a transducer if a transformer is given in list position.
*
* @func
* @memberOf R
* @since v0.20.0
* @category List
* @sig ((a, b) -> a) -> a -> (b -> String) -> [b] -> {String: a}
* @param {Function} valueFn The function that reduces the elements of each group to a single
* value. Receives two values, accumulator for a particular group and the current element.
* @param {*} acc The (initial) accumulator value for each group.
* @param {Function} keyFn The function that maps the list's element into a key.
* @param {Array} list The array to group.
* @return {Object} An object with the output of `keyFn` for keys, mapped to the output of
* `valueFn` for elements which produced that key when passed to `keyFn`.
* @see R.groupBy, R.reduce
* @example
*
* const groupNames = (acc, {name}) => acc.concat(name)
* const toGrade = ({score}) =>
* score < 65 ? 'F' :
* score < 70 ? 'D' :
* score < 80 ? 'C' :
* score < 90 ? 'B' : 'A'
*
* var students = [
* {name: 'Abby', score: 83},
* {name: 'Bart', score: 62},
* {name: 'Curt', score: 88},
* {name: 'Dora', score: 92},
* ]
*
* reduceBy(groupNames, [], toGrade, students)
* //=> {"A": ["Dora"], "B": ["Abby", "Curt"], "F": ["Bart"]}
*/
var reduceBy = _curryN(4, [], _dispatchable([], _xreduceBy,
function reduceBy(valueFn, valueAcc, keyFn, list) {
return _reduce(function(acc, elt) {
var key = keyFn(elt);
acc[key] = valueFn(_has(key, acc) ? acc[key] : _clone(valueAcc, [], [], false), elt);
return acc;
}, {}, list);
}));
/**
* Counts the elements of a list according to how many match each value of a
* key generated by the supplied function. Returns an object mapping the keys
* produced by `fn` to the number of occurrences in the list. Note that all
* keys are coerced to strings because of how JavaScript objects work.
*
* Acts as a transducer if a transformer is given in list position.
*
* @func
* @memberOf R
* @since v0.1.0
* @category Relation
* @sig (a -> String) -> [a] -> {*}
* @param {Function} fn The function used to map values to keys.
* @param {Array} list The list to count elements from.
* @return {Object} An object mapping keys to number of occurrences in the list.
* @example
*
* const numbers = [1.0, 1.1, 1.2, 2.0, 3.0, 2.2];
* R.countBy(Math.floor)(numbers); //=> {'1': 3, '2': 2, '3': 1}
*
* const letters = ['a', 'b', 'A', 'a', 'B', 'c'];
* R.countBy(R.toLower)(letters); //=> {'a': 3, 'b': 2, 'c': 1}
*/
var countBy = reduceBy(function(acc, elem) { return acc + 1; }, 0);
exports.countBy = countBy;
Object.defineProperty(exports, '__esModule', { value: true });
})));