Safari sort() function doesnt work - javascript

Why does my code not work correctly in the Safari browser on Iphone 6 ios 10 and above. In the support table, all values used in the code are supported! The code works everywhere except this device. For my data i use Wilddog it same work as Firebase. Array look like {name: 'Some', like: 2, fav_count: 5 }, {name: 'Some2', like: 3, fav_count: 4 }, {name: 'Some3', like: 3, fav_count: 4 }. Something wrong going on sort() function;
var obj = $wilddogObject(ref); // get data from server
obj.$loaded()
.then(function(data) {
var _extends = Object.assign || function(target) {
for (var i = 1; i < arguments.length; i++) {
var source = arguments[i];
for (var key in source) {
if (Object.prototype.hasOwnProperty.call(source, key)) { target[key] = source[key]; } } }
return target; };
var moments = _.map(data, function(val, id) {
return _extends({}, val, {
id: id
});
});
$scope.ratePlaces = _.map(moments, function(place) {
// console.log(place);
if (place != null) {
if (place.like != undefined) {
function rating(like, favs) {
var parseFavs = parseInt(favs);
var parseLike = parseInt(like);
var newRate = parseLike * 0.5 + parseFavs;
return newRate;
}
place.rate = rating(place.like, place.fav_count);
}
}
return place
})
console.log($scope.ratePlaces);
list($scope.ratePlaces)
})
function list(r) {
r.shift();
r.shift();
r.shift();
r.sort((a, b) => {
if (a.rate != null || a.rate != undefined || a.rate != 'daylife' || !a.name) {
return a.rate - b.rate;
} else {}
})
r.sort((a, b) => {
if (a.rate != null || a.rate != undefined || a.rate != 'daylife' || !a.name) {
let rateA = a.rate;
let rateB = b.rate;
if (rateA < rateB) {
return -1;
}
if (rateA > rateB) {
return 1;
}
return 0;
}
});
$scope.posts = r.reverse();

Related

The function set fails to update a non existant path under an existing key

See online playground link: https://repl.it/repls/ChocolateHummingMacroinstruction
I have a function that sets a deep nested property:
const rePropName = /[^.[\]]+|\[(?:(-?\d+(?:\.\d+)?)|(["'])((?:(?!\2)[^\\]|\\.)*?)\2)\]|(?=(?:\.|\[\])(?:\.|\[\]|$))/g;
const reIsUint = /^(?:0|[1-9]\d*)$/;
function isIndex(value, length = Number.POSITIVE_INFINITY) {
const isNumberLike = (value) => typeof value == 'number' || (typeof value != 'symbol' && reIsUint.test(value));
return isNumberLike(value) && (value > -1 && value % 1 == 0 && value < length);
}
function stringToPath (string) {
const result = [];
if (string.charCodeAt(0) === 46 /* . */) {
result.push('');
}
string.replace(rePropName, function(match, number, quote, subString) {
result.push(quote ? subString.replace(reEscapeChar, '$1') : (number || match));
});
return result;
}
function set(object, path, value) {
path = stringToPath(path);
const length = path.length;
const lastIndex = length - 1;
let index = -1;
let nested = object;
while (nested && ++index < length) {
const key = path[index];
let newValue = value;
if (index !== lastIndex) {
const objValue = nested[key];
if (value != null && typeof value == 'object') {
newValue = objValue;
} else if (isIndex(path[index + 1])) {
newValue = [];
} else {
newValue = {};
}
}
const isNotToBeUpdated = (object, key, value) => object.hasOwnProperty(key) &&
object[key] === value ||
(value === undefined && !(key in object));
if (!isNotToBeUpdated(nested, key, newValue)) {
nested[key] = newValue;
}
nested = nested[key];
}
return object;
}
Given that I have an object that looks like this:
const obj = {
the: {
dog: {
and: {
fox: 123
}
}
}
};
set(obj, 'the.war.of.wolf', 456);
It clobbers the existing value of the key and replaces it with the new value:
{
the: {
war: {
of: {
wolf: 456
}
}
}
}
Instead, I would like for it to update the nested property without destroying the existing value:
{
the: {
dog: {
and: {
fox: 123
}
},
war: {
of: {
wolf: 456
}
}
}
}

Factory pattern within Angular?

Someone mentioned I should use a true Factory pattern below so I don't have to constantly supply the typeName. How can this be accomplished within JavaScript and Angular. If it were C#, I wouldn't have a problem, but the Java reference / value types and Angular are making my brain hurt.
(function () {
'use strict';
angular
.module('blocks.object-cache');
objectCache.$inject = ['CacheFactory', '$auth'];
function objectCache(CacheFactory, $auth) {
var _options = {
maxAge : (60 * 60 * 1000),
deleteOnExpire : 'passive',
storageMode : 'localStorage'
};
var service = {
setOptions : setOptions,
getCache : getCache,
clear : clear,
getAll : getAll,
getItem : getItem,
getItems : getItems,
putItem : putItem,
putItems : putItems,
getItemsByKey : getItemsByKey,
getItemByKeyFirst : getItemByKeyFirst,
getItemByKeySingle : getItemByKeySingle,
removeItemsByKey : removeItemsByKey,
removeItemByKey : removeItemByKey,
putItemsByKey : putItemsByKey,
putItemByKey : putItemByKey
};
return service;
////////////////////////////////////////////////////////////////////////////////
function setOptions (options) {
options = options || {};
options.maxAge = options.maxAge = _options.maxAge;
options.deleteOnExpire = options.deleteOnExpire = _options.deleteOnExpire;
options.storageMode = options.storageMode = _options.storageMode;
_options = options;
}
function getCache(typeName) {
var cacheName = [getUserId(), normalizeTypeName(typeName || 'objects')].join('_');
var cache = CacheFactory(cacheName);
if (cache) { return cache; }
cache = CacheFactory(cacheName, _options);
return cache;
}
function clear (typeName) {
var cache = getCache(typeName);
cache.removeAll();
return (!cache.keys() || (cache.keys().length < 1));
}
function getAll (typeName) {
var cache = getCache(typeName);
var result = [];
(cache.keys() || []).forEach(function(key){
result.push(cache(key));
});
return result;
}
function getItem(typeName, id) {
if (typeof id == 'undefined' || !id.trim) { return null; }
var cache = getCache(typeName);
return cache.get(id);
}
function getItems(typeName, ids) {
var cache = getCache(typeName),
result = [],
_ids = [];
(ids || []).forEach(function(id){
if (_ids.indexOf(id) < 0) {
_ids.push(id);
var item = cache.get(id);
if (item) { result.push(item); }
}
});
return result;
}
function putItem(typeName, item, id, refresh) {
if (typeof item == 'undefined') { return false; }
if (typeof id == 'undefined' || !id.trim) { return false; }
var cache = getCache(typeName);
var existing = cache.get(id);
if (existing && !refresh) { return true; }
if (existing) { cache.remove(id); }
cache.put(item, id);
return (!!cache.get(id));
}
function putItems(typeName, items, idField, refresh) {
var cache = getCache(typeName);
(items || []).forEach(function(item){
var id = item[idField];
if (typeof id != 'undefined') {
var existing = cache.get(id);
if (existing && !!refresh) { cache.remove(id); }
if (!existing || !!refresh) { cache.put(item, id); }
if (!cache.get(id)) { return false; }
}
});
return true;
}
function getItemsByKey(typeName, key, value, isCaseSensitive) {
var result = [];
(getAll(typeName) || []).forEach(function(item){
var itemValue = item[key];
if (typeof itemValue != 'undefined') {
if ((typeof value == 'string') && (typeof itemValue == 'string') && (!isCaseSensitive || value.toLowerCase() == itemValue.toLowerCase())) {
result.push(item);
} else if (((typeof value) == (typeof itemValue)) && (value == itemValue)) {
result.push(item);
} else {
// Other scenarios?
}
}
});
return result;
}
function getItemByKeyFirst(typeName, key, value, isCaseSensitive) {
var items = getItemsByKey(typeName, key, value, isCaseSensitive) || [];
return (items.length > 0) ? items[0] : null;
}
function getItemByKeySingle(typeName, key, value, isCaseSensitive) {
var items = getItemsByKey(typeName, key, value, isCaseSensitive) || [];
return (items.length === 0) ? items[0] : null;
}
function removeItemsByKey (typeName, keyField, values, isCaseSensitive) {
var cache = getCache(typeName),
keysToRemove = [];
(cache.keys() || []).forEach(function(key){
var item = cache.get[key],
itemValue = item[keyField];
if (typeof itemValue != 'undefined') {
for (var v = 0; v < (values || []).length; v += 1) {
if ((typeof values[v] == 'string') && (typeof itemValue == 'string') && (!isCaseSensitive || values[v].toLowerCase() == itemValue.toLowerCase())) {
keysToRemove.push(key);
break;
} else if (((typeof values[v]) == (typeof itemValue)) && (values[v] == itemValue)) {
keysToRemove.push(key);
break;
} else {
// Other scenarios?
}
}
}
});
var success = true;
keysToRemove.forEach(function(key){
cache.remove(key);
if (cache.get(key)) { success = false; }
});
return success;
}
function removeItemByKey (typeName, keyField, value, isCaseSensitive) {
return removeItemsByKey(typeName, keyField, [value], isCaseSensitive);
}
function putItemsByKey(typeName, items, keyField, refresh, isCaseSensitive) {
if (!!refresh) {
var values = _.map((items || []), keyField);
if (!removeItemsByKey(typeName, keyField, values, isCaseSensitive)) { return false; }
}
var cache = getCache(typeName);
(items || []).forEach(function(item){
var id = item[keyField];
if (typeof value != 'undefined') { cache.put(item, id); }
if (!cache.get(id)) { return false; }
});
return true;
}
function putItemByKey(typeName, item, keyField, refresh, isCaseSensitive) {
return putItemsByKey(typeName, [item], keyField, refresh, isCaseSensitive);
}
function getUserId () {
return $auth.isAuthenticated() ? ($auth.getPayload().sub || 'unknown') : 'public';
}
function normalizeTypeName (typeName) {
return typeName.split('.').join('-');
}
}
})();
I'm not an Angular guru, but couldn't you just move the functions to achieve a factory-like pattern? I have not tested this, but with about two minutes of copy-n-paste...
Edit: Removed your nested iterate functions.
(function () {
'use strict';
angular
.module('blocks.object-cache')
.service('ObjectCache', ObjectCache);
ObjectCache.$inject = ['CacheFactory', '$auth'];
function ObjectCache(CacheFactory, $auth) {
var _options = {
maxAge : (60 * 60 * 1000),
deleteOnExpire : 'passive',
storageMode : 'localStorage'
};
var factory = {
getCache : getCache
};
return factory;
////////////////////////////
function getCache(typeName, options) {
options = options || {};
options.maxAge = options.maxAge = _options.maxAge;
options.deleteOnExpire = options.deleteOnExpire = _options.deleteOnExpire;
options.storageMode = options.storageMode = _options.storageMode;
typeName = normalizeTypeName(typeName || 'objects');
var userId = getUserId() || 'public';
var name = userId + '_' + typeName;
var service = {
type : typeName,
user : userId,
name : name,
options : options,
cache : CacheFactory(name) || CacheFactory.createCache(name, options),
clear : function () {
this.cache.removeAll();
},
getAll : function () {
var result = [];
var keys = this.cache.keys() || [];
for (var i = 0; i < keys.length; i += 1) {
result.push(this.cache(keys[i]));
}
return result;
},
getItems : function (ids) {
var result = [],
_ids = [];
for (var i = 0; i < (ids || []).length; i += 1) {
var id = ids[i];
if (_ids.indexOf(id) < 0) {
_ids.push(id);
var item = this.cache.get(id);
if (item) { result.push(item); }
}
}
return result;
},
getItem : function (id) {
var items = this.getItems([id]);
return (items.length > 0) ? items[0] : null;
},
putItem : function (item, id, refresh) {
var existing = this.cache.get(id);
if (existing && !refresh) { return true; }
if (existing) { this.cache.remove(id); }
this.cache.put(item, id);
return (!!this.cache.get(id));
},
putItems : function (items, idField, refresh) {
var success = true;
for (var i = 0; i < (items || []).length; i += 1) {
var item = items[i];
var id = item[idField];
if (typeof id != 'undefined') {
if (this.putItem(item, id, refresh)) { success = false; }
}
}
return success;
},
getItemsByKey : function (key, value, isCaseSensitive) {
var result = [];
(this.getAll() || []).forEach(function(item){
var itemValue = item[key];
if (typeof itemValue != 'undefined') {
if ((typeof value == 'string') && (typeof itemValue == 'string') && (!isCaseSensitive || value.toLowerCase() == itemValue.toLowerCase())) {
result.push(item);
} else if (((typeof value) == (typeof itemValue)) && (value == itemValue)) {
result.push(item);
} else {
// Other scenarios?
}
}
});
return result;
},
getItemByKeyFirst : function (key, value, isCaseSensitive) {
var items = this.getItemsByKey(key, value, isCaseSensitive) || [];
return (items.length > 0) ? items[0] : null;
},
getItemByKeySingle : function (key, value, isCaseSensitive) {
var items = this.getItemsByKey(key, value, isCaseSensitive) || [];
return (items.length === 0) ? items[0] : null;
},
removeItemsByKey : function (keyField, values, isCaseSensitive) {
var keysToRemove = [],
keys = this.cache.keys() || [];
for (var k = 0; k < keys.length; k += 1) {
var key = keys[k];
var item = this.cache.get(key);
var itemVal = item[keyField];
if (typeof itemVal != 'undefined') {
for (var v = 0; v < (values || []).length; v += 1) {
if ((typeof values[v] == 'string') && (typeof itemVal == 'string') && (!isCaseSensitive || values[v].toLowerCase() == itemVal.toLowerCase())) {
keysToRemove.push(key);
break;
} else if (((typeof values[v]) == (typeof itemVal)) && (values[v] == itemVal)) {
keysToRemove.push(key);
break;
} else {
// Other scenarios?
}
}
}
}
var success = true;
for (var r = 0; r < keysToRemove.length; r += 1) {
this.cache.remove(keysToRemove[r]);
if (this.cache.get(keysToRemove[r])) { success = false; }
}
return success;
},
removeItemByKey : function (keyField, value, isCaseSensitive) {
return this.removeItemsByKey(keyField, [value], isCaseSensitive);
},
putItemsByKey : function(items, keyField, refresh, isCaseSensitive) {
if (!!refresh) {
var values = _.map((items || []), keyField);
if (!this.removeItemsByKey(keyField, values, isCaseSensitive)) { return false; }
}
for (var i = 0; i < (items || []).length; i += 1) {
var id = items[i][keyField];
if (typeof id != 'undefined') {
this.cache.put(items[i], id);
if (!this.cache.get(id)) { return false; }
}
}
return true;
},
putItemByKey : function (item, keyField, refresh, isCaseSensitive) {
return this.putItemsByKey([item], keyField, refresh, isCaseSensitive);
}
};
return service;
}
function getUserId () {
return $auth.isAuthenticated() ? ($auth.getPayload().sub || 'unknown') : null;
}
function normalizeTypeName (typeName) {
return typeName.split('.').join('-');
}
}
})();

Code works with arrays, but not multidimensional arrays.

Working on a Holdem hand evaluator, and part of the yak shaving is writing a "how many combos of 5 do you get from 7 cards" function (pickNofSet()). I've done that, but the way I've done that returns a bunch of duplicates.
So I have to write a removeDuplicates(). Here's the problem... it works with a simple array, but it doesn't work with the "arrays of arrays" that my "pickNofSet" function generates.
-- here's the removeDuplicates code --
var removeDuplicates = function(input){ // takes array
var output = [];
for (i=0; i < input.length; i++){
var unique = true; // all elements are innocent until proven guilty
for(j=i+1; j < input.length; j++){
if(input[j] === input[i]){
unique = false; // guilty!
};// endif
};// end jfor
if(unique){ // if not found guilty,
output.push(input[i]); // you may go free, little element
};// end if
};// end ifor
console.log(output);
return output; };//end function
Here's what I get from the Console:
> removeDuplicates(['a','b','c'],['a','b','c'],['d','e','f'],['g','h','i']);
< undefined
> removeDuplicates([1, 2, 2, 3, 3, 5, 5, 6, 6, 6]);
< [1, 2, 3, 5, 6]
Operator === can't compare array
As you use === to check equality between two elements, this only works with primitive data types, but not array. e.g.
1===1 // true
[1]===[1] // Sorry, you can't
If you want your algorithm to work with both primitive elements and array elements, you may need to upgrade your equality check from === to a customized function.
From this:
if(input[j] === input[i]){
unique = false; // guilty!
};// endif
To this:
if (equals(input[j],input[i]){
unique = false; // guilty!
};// endif
And implement equals function to be capable of comparing both primitive data types and arrays:
function equals(a,b){
if (typeof(a)!=typeof(b))
return false;
else if (typeof(a)=='object'){
if (Object.keys(a).length != Object.keys(b).length)
return false;
else{
for (var keyA of Object.keys(a)){
if (!(keyA in b))
return false;
else if (a[keyA]!==b[keyA])
return false;
else
return true;
}
}
}
else
return a===b;
}
Hint: This solution should, hopefully, also work with JSON element.
Here is an example of a general purpose unique filter that should fill your need. Requires an ES5 compliant environment.
(function () {
'use strict';
function $strictEqual(a, b) {
return a === b;
}
function $isUndefined(inputArg) {
return $strictEqual(typeof inputArg, 'undefined');
}
function $isPrimitive(inputArg) {
var type = typeof inputArg;
return type === 'undefined' || inputArg === null || type === 'boolean' || type === 'string' || type === 'number' || type === 'symbol';
}
function $isFunction(inputArg) {
return typeof inputArg === 'function';
}
function $isDate(inputArg) {
return Object.prototype.toString.call(inputArg) === '[object Date]';
}
function $isRegExp(inputArg) {
return Object.prototype.toString.call(inputArg) === '[object RegExp]';
}
function $isString(inputArg) {
return Object.prototype.toString.call(inputArg) === '[object String]';
}
function $isArguments(inputArg) {
return Object.prototype.toString.call(inputArg) === '[object Arguments]';
}
function $getItem(object, index) {
var item;
if ($isString(object)) {
item = object.charAt(index);
} else {
item = object[index];
}
return item;
}
var de = function (a, b, circ) {
if (a === b) {
return true;
}
var aType,
bType,
aIsArgs,
bIsArgs,
aIsPrim,
bIsPrim,
aCirc,
bCirc,
ka,
kb,
length,
index,
it;
if ($isDate(a) && $isDate(b)) {
return a.getTime() === b.getTime();
}
if ($isRegExp(a) && $isRegExp(b)) {
return a.source === b.source &&
a.global === b.global &&
a.multiline === b.multiline &&
a.lastIndex === b.lastIndex &&
a.ignoreCase === b.ignoreCase &&
a.sticky === b.sticky;
}
aIsPrim = $isPrimitive(a);
bIsPrim = $isPrimitive(b);
if ((aIsPrim || $isFunction(a)) && (bIsPrim || $isFunction(b))) {
/*jslint eqeq: true */
return a == b;
}
if (aIsPrim || bIsPrim) {
return a === b;
}
if (a.prototype !== b.prototype) {
return false;
}
if (circ.a.indexOf(a) === -1) {
circ.a.push(a);
} else {
aCirc = true;
}
if (circ.b.indexOf(b) === -1) {
circ.b.push(b);
} else {
bCirc = true;
}
if (aCirc && bCirc) {
circ.cnt += 1;
} else {
circ.cnt = 0;
}
if (circ.cnt > 200) {
throw new RangeError('Circular reference limit exceeded');
}
aIsArgs = $isArguments(a);
bIsArgs = $isArguments(b);
if ((aIsArgs && !bIsArgs) || (!aIsArgs && bIsArgs)) {
return false;
}
if (aIsArgs) {
return de(Array.prototype.slice.call(a), Array.prototype.slice.call(b), circ);
}
ka = Object.keys(a);
kb = Object.keys(b);
length = ka.length;
if (length !== kb.length) {
if (Array.isArray(a) && Array.isArray(b)) {
if (a.length !== b.length) {
return false;
}
} else {
return false;
}
} else {
ka.sort();
kb.sort();
for (index = 0; index < length; index += 1) {
if (ka[index] !== kb[index]) {
return false;
}
}
}
for (index = 0; index < length; index += 1) {
it = ka[index];
if (!de($getItem(a, it), $getItem(b, it), circ)) {
return false;
}
}
aType = typeof a;
bType = typeof b;
return aType === bType;
};
if (!Object.prototype.deepEqual) {
Object.defineProperty(Object.prototype, 'deepEqual', {
enumerable: false,
configurable: true,
writable: true,
value: function (b) {
var a = this;
return de(a, b, {
a: [],
b: [],
cnt: 0
});
}
});
}
if (!Array.prototype.unique) {
Object.defineProperty(Array.prototype, 'unique', {
enumerable: false,
configurable: true,
writable: true,
value: function (equalFn, thisArg) {
var object = Object(this),
length,
index,
eqFn,
arr,
idx,
val,
it;
if ($isUndefined(equalFn)) {
eqFn = $strictEqual;
} else {
eqFn = equalFn;
}
if (!$isFunction(eqFn)) {
throw new TypeError('Argument is not a function: ' + eqFn);
}
arr = [];
length = object.length >>> 0;
for (index = 0; index < length; index += 1) {
if (index in object) {
it = $getItem(object, index);
val = true;
for (idx = 0; idx < length; idx += 1) {
if (idx < index && idx in object && eqFn.call(thisArg, it, $getItem(object, idx))) {
val = false;
break;
}
}
if (val) {
arr.push(it);
}
}
}
return arr;
}
});
}
}());
var data1 = [1, 2, 2, 3, 3, 5, 5, 6, 6, 6],
data2 = [
['a', 'b', 'c'],
['a', 'b', 'c'],
['d', 'e', 'f'],
['g', 'h', 'i']
],
equals = Function.prototype.call.bind(Object.prototype.deepEqual),
pre = document.getElementById('out');
pre.textContent = JSON.stringify(data1.unique(equals), null, 2);
pre.textContent += '\n\n';
pre.textContent += JSON.stringify(data2.unique(equals), null, 2);
<pre id="out"></pre>

Easy way to get multi-level javascript object property

I always need to deal with multi-level js objects where existence of properties are not certain:
try { value1 = obj.a.b.c; } catch(e) { value1 = 1; }
try { value2 = obj.d.e.f; } catch(e) { value2 = 2; }
......
Is there an easier way or a generic function (e.g. ifnull(obj.d.e.f, 2) ) that does not require a lot of try catches?
var value1 = (obj.a && obj.a.b && obj.a.b.c) || 1;
http://jsfiddle.net/DerekL/UfJEQ/
Or use this:
function ifNull(obj, key, defVal){
var keys = key.split("."), value;
for(var i = 0; i < keys.length; i++){
if(typeof obj[keys[i]] !== "undefined"){
value = obj = obj[keys[i]];
}else{
return defVal;
}
}
return value;
}
var value1 = ifNull(obj, "a.b.c", 1);
You could always create a helper function.
function isUndefined(root, path, defaultVal) {
var parts = path.split('.'),
i = 0,
len = parts.length,
o = root || {}, v;
while ((typeof (v = o[parts[i]]) === 'object', o = v) && ++i < len);
return (typeof v === 'undefined' || i !== len)? defaultVal: v;
}
var obj = {a: { b: { test: 'test' }}}, v;
v = isUndefined(obj, 'a.b.test', 1); //test
v = isUndefined(obj, 'a.test', 1); //1
Using lodash you can do this easily**(node exists and empty check for that node)**..
var lodash = require('lodash-contrib');
function invalidateRequest(obj, param) {
var valid = true;
param.forEach(function(val) {
if(!lodash.hasPath(obj, val)) {
valid = false;
} else {
if(lodash.getPath(obj, val) == null || lodash.getPath(obj, val) == undefined || lodash.getPath(obj, val) == '') {
valid = false;
}
}
});
return valid;
}
Usage:
leaveDetails = {
"startDay": 1414998000000,
"endDay": 1415084400000,
"test": { "test1" : 1234 }
};
var validate;
validate = invalidateRequest(leaveDetails, ['startDay', 'endDay', 'test.test1']);
it will return boolean.

JS: How to return 'undefined' instead of throwing error 'cannot read property x of undefined'

What is the best way to have js return undefined rather than throw an error when a parent property does not exist?
Example
a = {}
b = a.x.y.z
// Error: Cannot read property 'value' of undefined
// Target result: b = undefined
You have to check for the existence of each property:
var b;
if (a.x && a.x.y && a.x.y.z) {
b = a.x.y.z
}
Or, simliar to another poster's "safeGet" function:
var get = function (obj, ns) {
var y = ns.split('.');
for(var i = 0; i < y.length; i += 1) {
if (obj[y[i]]) {
obj = obj[y[i]];
} else {
return;
}
}
return obj;
};
Use:
var b = get(a, 'x.y.z');
try {
a = {}
b = a.x.y.z
}
catch (e) {
b = void 0;
}
I would go for slightly verbose:
var b = ((a.x || {}).y || {}).z
you could write a safeGet helper function, something like:
edited for drilldown as suggested in comments by arcyqwerty
var getter = function (collection, key) {
if (collection.hasOwnProperty(key)) {
return collection[key];
} else {
return undefined;
}
};
var drillDown = function (keys, currentIndex, collection) {
var max = keys.length - 1;
var key = keys[currentIndex];
if (typeof collection === 'undefined') {
return undefined;
}
if (currentIndex === max) {
return getter(collection, key);
} else {
return drillDown(keys, currentIndex + 1,
getter(collection, key));
}
};
var safeGet = function (collection, key) {
if (key.indexOf(".") !== -1) {
return drillDown(key.split("."), 0, collection);
} else {
return getter(collection, key);
}
};
a = { x: 1 };
b = safeGet(a, 'x.y.z');
http://jsfiddle.net/YqdWH/2/

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