leaflet/src/core/Util.js

JavaScript library for mobile-friendly interactive maps

/*
 * @namespace Util
 *
 * Various utility functions, used by Leaflet internally.
 */

// @function extend(dest: Object, src?: Object): Object
// Merges the properties of the `src` object (or multiple objects) into `dest` object and returns the latter. Has an `L.extend` shortcut.
export function extend(dest) {
	var i, j, len, src;

	for (j = 1, len = arguments.length; j < len; j++) {
		src = arguments[j];
		for (i in src) {
			dest[i] = src[i];
		}
	}
	return dest;
}

// @function create(proto: Object, properties?: Object): Object
// Compatibility polyfill for [Object.create](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object/create)
export var create = Object.create || (function () {
	function F() {}
	return function (proto) {
		F.prototype = proto;
		return new F();
	};
})();

// @function bind(fn: Function, …): Function
// Returns a new function bound to the arguments passed, like [Function.prototype.bind](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Function/bind).
// Has a `L.bind()` shortcut.
export function bind(fn, obj) {
	var slice = Array.prototype.slice;

	if (fn.bind) {
		return fn.bind.apply(fn, slice.call(arguments, 1));
	}

	var args = slice.call(arguments, 2);

	return function () {
		return fn.apply(obj, args.length ? args.concat(slice.call(arguments)) : arguments);
	};
}

// @property lastId: Number
// Last unique ID used by [`stamp()`](#util-stamp)
export var lastId = 0;

// @function stamp(obj: Object): Number
// Returns the unique ID of an object, assigning it one if it doesn't have it.
export function stamp(obj) {
	if (!('_leaflet_id' in obj)) {
		obj['_leaflet_id'] = ++lastId;
	}
	return obj._leaflet_id;
}

// @function throttle(fn: Function, time: Number, context: Object): Function
// Returns a function which executes function `fn` with the given scope `context`
// (so that the `this` keyword refers to `context` inside `fn`'s code). The function
// `fn` will be called no more than one time per given amount of `time`. The arguments
// received by the bound function will be any arguments passed when binding the
// function, followed by any arguments passed when invoking the bound function.
// Has an `L.throttle` shortcut.
export function throttle(fn, time, context) {
	var lock, args, wrapperFn, later;

	later = function () {
		// reset lock and call if queued
		lock = false;
		if (args) {
			wrapperFn.apply(context, args);
			args = false;
		}
	};

	wrapperFn = function () {
		if (lock) {
			// called too soon, queue to call later
			args = arguments;

		} else {
			// call and lock until later
			fn.apply(context, arguments);
			setTimeout(later, time);
			lock = true;
		}
	};

	return wrapperFn;
}

// @function wrapNum(num: Number, range: Number[], includeMax?: Boolean): Number
// Returns the number `num` modulo `range` in such a way so it lies within
// `range[0]` and `range[1]`. The returned value will be always smaller than
// `range[1]` unless `includeMax` is set to `true`.
export function wrapNum(x, range, includeMax) {
	var max = range[1],
	    min = range[0],
	    d = max - min;
	return x === max && includeMax ? x : ((x - min) % d + d) % d + min;
}

// @function falseFn(): Function
// Returns a function which always returns `false`.
export function falseFn() { return false; }

// @function formatNum(num: Number, precision?: Number|false): Number
// Returns the number `num` rounded with specified `precision`.
// The default `precision` value is 6 decimal places.
// `false` can be passed to skip any processing (can be useful to avoid round-off errors).
export function formatNum(num, precision) {
	if (precision === false) { return num; }
	var pow = Math.pow(10, precision === undefined ? 6 : precision);
	return Math.round(num * pow) / pow;
}

// @function trim(str: String): String
// Compatibility polyfill for [String.prototype.trim](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String/Trim)
export function trim(str) {
	return str.trim ? str.trim() : str.replace(/^\s+|\s+$/g, '');
}

// @function splitWords(str: String): String[]
// Trims and splits the string on whitespace and returns the array of parts.
export function splitWords(str) {
	return trim(str).split(/\s+/);
}

// @function setOptions(obj: Object, options: Object): Object
// Merges the given properties to the `options` of the `obj` object, returning the resulting options. See `Class options`. Has an `L.setOptions` shortcut.
export function setOptions(obj, options) {
	if (!Object.prototype.hasOwnProperty.call(obj, 'options')) {
		obj.options = obj.options ? create(obj.options) : {};
	}
	for (var i in options) {
		obj.options[i] = options[i];
	}
	return obj.options;
}

// @function getParamString(obj: Object, existingUrl?: String, uppercase?: Boolean): String
// Converts an object into a parameter URL string, e.g. `{a: "foo", b: "bar"}`
// translates to `'?a=foo&b=bar'`. If `existingUrl` is set, the parameters will
// be appended at the end. If `uppercase` is `true`, the parameter names will
// be uppercased (e.g. `'?A=foo&B=bar'`)
export function getParamString(obj, existingUrl, uppercase) {
	var params = [];
	for (var i in obj) {
		params.push(encodeURIComponent(uppercase ? i.toUpperCase() : i) + '=' + encodeURIComponent(obj[i]));
	}
	return ((!existingUrl || existingUrl.indexOf('?') === -1) ? '?' : '&') + params.join('&');
}

var templateRe = /\{ *([\w_ -]+) *\}/g;

// @function template(str: String, data: Object): String
// Simple templating facility, accepts a template string of the form `'Hello {a}, {b}'`
// and a data object like `{a: 'foo', b: 'bar'}`, returns evaluated string
// `('Hello foo, bar')`. You can also specify functions instead of strings for
// data values — they will be evaluated passing `data` as an argument.
export function template(str, data) {
	return str.replace(templateRe, function (str, key) {
		var value = data[key];

		if (value === undefined) {
			throw new Error('No value provided for variable ' + str);

		} else if (typeof value === 'function') {
			value = value(data);
		}
		return value;
	});
}

// @function isArray(obj): Boolean
// Compatibility polyfill for [Array.isArray](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array/isArray)
export var isArray = Array.isArray || function (obj) {
	return (Object.prototype.toString.call(obj) === '[object Array]');
};

// @function indexOf(array: Array, el: Object): Number
// Compatibility polyfill for [Array.prototype.indexOf](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array/indexOf)
export function indexOf(array, el) {
	for (var i = 0; i < array.length; i++) {
		if (array[i] === el) { return i; }
	}
	return -1;
}

// @property emptyImageUrl: String
// Data URI string containing a base64-encoded empty GIF image.
// Used as a hack to free memory from unused images on WebKit-powered
// mobile devices (by setting image `src` to this string).
export var emptyImageUrl = 'data:image/gif;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=';

// inspired by https://paulirish.com/2011/requestanimationframe-for-smart-animating/

function getPrefixed(name) {
	return window['webkit' + name] || window['moz' + name] || window['ms' + name];
}

var lastTime = 0;

// fallback for IE 7-8
function timeoutDefer(fn) {
	var time = +new Date(),
	    timeToCall = Math.max(0, 16 - (time - lastTime));

	lastTime = time + timeToCall;
	return window.setTimeout(fn, timeToCall);
}

export var requestFn = window.requestAnimationFrame || getPrefixed('RequestAnimationFrame') || timeoutDefer;
export var cancelFn = window.cancelAnimationFrame || getPrefixed('CancelAnimationFrame') ||
		getPrefixed('CancelRequestAnimationFrame') || function (id) { window.clearTimeout(id); };

// @function requestAnimFrame(fn: Function, context?: Object, immediate?: Boolean): Number
// Schedules `fn` to be executed when the browser repaints. `fn` is bound to
// `context` if given. When `immediate` is set, `fn` is called immediately if
// the browser doesn't have native support for
// [`window.requestAnimationFrame`](https://developer.mozilla.org/docs/Web/API/window/requestAnimationFrame),
// otherwise it's delayed. Returns a request ID that can be used to cancel the request.
export function requestAnimFrame(fn, context, immediate) {
	if (immediate && requestFn === timeoutDefer) {
		fn.call(context);
	} else {
		return requestFn.call(window, bind(fn, context));
	}
}

// @function cancelAnimFrame(id: Number): undefined
// Cancels a previous `requestAnimFrame`. See also [window.cancelAnimationFrame](https://developer.mozilla.org/docs/Web/API/window/cancelAnimationFrame).
export function cancelAnimFrame(id) {
	if (id) {
		cancelFn.call(window, id);
	}
}