Select global variable by string, including sub-properties - javascript

In javascript, I want to select a certain property by it's name, which is stored in a string. I know that window[someString] is the way to go. It works when someString = "somevariable", but unfortunately, my program will also have strings such as someobject.someproperty. This does not work.
So the question is, given code
someString = "one.two.three";
one = {
two: {
three: "This is the value that I want to get"
}
};
// window[someString] does not work.
, how can I get the value of one.two.three using the value of someString, without using eval?

Use split and make a recursive method
var someString = "one.two.three";
var keys = someString.split('.');
one = {
two: {
three: "This is the value that I want to get"
}
};
function getinnerProperty(object, keys) {
var key = keys.shift();
if (keys.length) {
var nestedObject = object[key];
return getinnerProperty(nestedObject, keys);
} else {
return object[key];
}
}
console.log(getinnerProperty(window, keys));

You can write a function that uses split and iteratively traverses the object tree:
var someString = "one.two.three";
var one = {
two: {
three: "This is the value that I want to get"
}
};
function getValue(keyStr) {
var keys = keyStr.split('.');
var result = global;
for (var i = 0; i < keys.length; i++) {
result = result[keys[i]];
}
return result != global ? result : undefined;
}
getValue(someString);

Related

Why are my results different when using a literal string versus a local variable

I have the following loop.
for (var key in criteria) {
var exists = Object.keys(item).some(function(k) {
return item[k] === "Test";
})
}
This works perfectly. And I get a 15 trues based on the number of items. However if I change it to the following:
for (var key in criteria) {
var myString = item[key];
var exists = Object.keys(item).some(function(k) {
return item[k] === myString;
});
}
Where I know the item[key] will equate to "Test" at some point in my loop, it does not produce the same result. In fact it returns all trues,
Criteria is an object that is like this:
{
habitat_type: "Mangroves",
issue_specific_terms: "Test"
}
Item is also an object like:
{
habitat_type: "Streams and rivers",
cci: "Low productivity/loss of agriculture",
intervention_type: "Restoration",
issue_specific_terms: "Test",
country: "United States of America"
}
You need to change what myString is - currently, it's always going to be equal because criteria doesn't come into it currently. Change myString to criteria[key]:
for (var key in criteria) {
var myString = criteria[key];
var exists = Object.keys(item).some(k => item[k] === myString);
}

Javascript Loop object and manipulate

I am working on a function where I pass an object (record) to a function. It then loops over the keys and checks to see if that key is in our second object (lookup). If there is a match, it replaces the value in our record with a manipulated version (turns it into a link). If there is no match, it keeps its original value.
This is what I am passing to the function:
{ Source: "1234", NTID: "joeBob", Department: "x123", Email: 'joebob#example.com' }
-Here is the function
function createLink2(record) {
// Link types
var output = {
'ntid': 'https://example.com/profile/',
'email': 'mailTo:'
};
// Vars
var i,
key,
keys = Object.keys(output);
// Loop over our object keys
Object.keys(record).forEach(function(k, ind) {
// Loop over each of the link types
for ( i = 0; i < keys.length; ++i ) {
key = keys[i];
// If our key matches that of our object, turn it into a link
if(k.toLowerCase() == key){
record = ''+record[k]+'';
}else{
// Return the original value of the property since its not a match. Not quite sure how to do this part.
}
}
});
return record;
}
My goal here is that it would replace the value of Email with joeBob#example.com and NTID with joeBob.
The issue I am having is with the return - Not quite sure how to edit the data and return the full object back.
change this line:
record = ''+record[k]+'';
to this:
record[k] = ''+record[k]+'';
Of course, you could do this more easily by referring to the properties of the object directly:
function createLink2(record) {
// Link types
var output = {
'NTID': 'https://example.com/profile/',
'Email': 'mailTo:'
};
// Loop over the output keys
Object.keys(output).forEach(function(k, ind) {
if(record.hasOwnProperty(k)) {
record[k] = '' + record[k] + '';
}
});
return record;
}
Note that you don't really need to return it since the contents of the object will be changed directly as mentioned by others in the comments.
Javascript objects are passed by reference. So if you modify the object in the function it will be enough. Example:
function test(obj) {
obj.a = 10
}
var x = {a: 2};
test(x);
console.log(x.a) //prints 10
So, all you have to do is modify the value of "Email" with whatever you want.
You can iterate over an array and return an object using .reduce()
function createLink2(record) {
// Link types
var output = {
'ntid': 'https://example.com/profile/',
'email': 'mailTo:'
};
// Vars
var keys = Object.keys(output);
// Loop over our object keys
record = keys.reduce(function(obj, currKey) {
if (obj[currKey] != undefined) {
obj[currKey] = '' + obj[currKey] + ''
}
return obj;
}, record);
return record;
}
console.log(createLink2({ntid: "12345", email: "joebob#gmail.com"}));

How to write a function that takes a string and object and interpolates that object in the string?

Hi everyone I need to write a function that takes a string and object and interpolates that object in the string so something like this
// interpolate("Its {weather} outside", {weather: 'damn Hot'})
// returns 'It's damn hot outside'
// interpolate( "Hi my name is {name}", {name: 'John'});
// returns 'Hi my name is John'
It should also no matter how deep the object goes so a case like this
// interpolate("Hi my name is {contact.name}", {contact: {name: 'john'}});
Im a little stuck and at first I tried splitting up the string into an array then trying to fit the object value in the array then join that back together but that has not worked for all test cases, can someone help me write this function and explain their solution please? Thankyou
so I tried something like this but does not really work for all test cases, this is a template literal but the function should just work giving those values as arguments on its own, otherwise I'm pretty stuck . .
function interpolate(strings, ...keys) {
return (function(...values) {
var dict = values[values.length - 1] || {};
var result = [strings[0]];
keys.forEach(function(key, i) {
var value = Number.isInteger(key) ? values[key] : dict[key];
result.push(value, strings[i + 1]);
});
return result.join('');
});
}
var t1Closure = interpolate`${0}${1}${0}!`;
t1Closure('Y', 'A'); // "YAY!"
var t2Closure = interpolate`${0} ${'foo'}!`;
console.log(t2Closure('Hello', {foo: 'World'})); // "Hello World!"
ok I'm getting closer so I separated the problem into two functions and need to combine them, the only thing is I'm not sure how to get the last use case to work without template literals
var something = "something";
var sub = function(str) {
return str.replace(/#\{(.*?)\}/g,
function(whole, expr) {
return eval(expr)
})
}
console.log(sub("hello #{something}"));
var objectValue = function(str, obj){
for(key in obj) {
if(obj.hasOwnProperty(key)) {
var value = obj[key];
return str + value;
}
}
}
console.log(objectValue("hi my name is ", {contact: {name: 'john'}}));
Using the dreaded eval
If you control the string that you pass and consider it safe, you can use eval:
function interpolate (str, obj) {
return str.replace(/\{(.*?)\}/g, function (_, ref) {
return eval('obj.' + ref);
});
}
var output = interpolate("Its {weather} outside", {weather: 'damn Hot'});
console.log(output);
output = interpolate("Hi my name is {contact.name}", {contact: {name: 'john'}});
console.log(output);
output = interpolate("The highest bid is {rank[0].bid}", {rank: [{bid: 900}, {bid:600}]});
console.log(output);
Be aware that if given a string like '{x;alert("hi")}', the above function would execute that alert, or any code that is put instead. So this is not a good solution if the string is provided (or can be altered) by the user.
Template Literals
It does not follow your function descriptor, but template literals already offer the functionality you are looking for:
var weather = 'damn Hot';
var output = `It's ${weather} outside`;
console.log(output);
var contact = {name: 'john'};
var output = `Hi my name is ${contact.name}`;
console.log(output);
Here you go:
'use strict';
function interpolate(str, obj) {
for (let prop in obj) {
if (obj.hasOwnProperty(prop)) {
str = str.replace(new RegExp(`{${prop}}`, 'g'), obj[prop]);
}
}
return str;
}
console.log(interpolate("Its {weather} outside", {weather: 'damn Hot'}));
// Its damn Hot outside
Try renderjs.
$("<p>Its {{:weather}} outside</p>").render({weather: 'damn Hot'})
-> <p>Its damn Hot outside</p>
Or lodash templates. Lodash already has a lot of handy features you end up using a lot of in my opinion.
var str = _.template('Its <%= weather %> outside')({weather: 'damn Hot'});
// If you wanted to use the {{:var}} syntax.
_.templateSettings.interpolate = /{{:([\s\S]+?)}}/g;
var str = _.template('Its {{:weather}} outside')({weather: 'damn Hot'});
A little late to the party, but in case you cannot (don't want to) use any external libraries or ES6, here is the idea:
function getMatches(s) {
var regExp = /{([^}]*)}/g,
matches = [],
match;
while ((match = regExp.exec(s)) != null) {
matches.push(match[1]);
}
return matches;
}
function objValue(obj, i) {
return obj[i];
}
function interpolate(s, obj) {
var matches = getMatches(s),
result = s;
matches.forEach(function (match) {
var props = match.split('.'),
value = props.reduce(objValue, obj) || '';
result = result.replace('{' + match + '}', value);
});
return result;
}
Usage
interpolate("Its {weather} outside", { weather: 'damn Hot' });
JSFiddle.

Can i use string as pointer in object in javascript? [duplicate]

var give = 'i.want.it';
var obj = {
i: {
want: {
it: 'Oh I know you do...'
}
}
};
console.log(obj[give]); // 'Oh I know you do...'
Can I somehow get the object string using a path String of some sort? I'm trying to store a relationship in a database where the field it can't be in it's own document.
Use Array#reduce() method
var give = 'i.want.it';
var obj = {
i: {
want: {
it: 'Oh I know you do...'
}
}
};
var res = give.split('.').reduce(function(o, k) {
return o && o[k];
}, obj);
console.log(res);
This will work :
var give = 'i.want.it';
var obj = {
i: {
want: {
it: 'Oh I know you do...'
}
}
};
console.log( eval("obj."+give));
Live DEMO JSFiddle
This is a really easy way to do it, but not safe, i don't advise you to use it for professional use. Use previous answer they looks good.
make it
var obj = {
i: {
want: {
it: 'Oh I know you do...'
}
}
};
//var result = JSON.parse(JSON.stringify(obj)); //cloning the existing obj
var result = obj; //cloning the existing obj
var give = 'i.want.it';
//now split the give and iterate through keys
give.split(".").forEach(function(key){
result = result[key];
});
console.log(result);
You can use eval()
var obj = {"a": { "b": { "c": 3}}};
writeln(eval('obj.a.b.c') + 2);
This will output 5.
JavaScript is weakly typed and thus it's evaluation function executes a statement as well as evaluating an expression.

Set of objects in javascript

I'd like to have a set of objects in Javascript. That is, a data structure that contains only unique objects.
Normally using properties is recommended, e.g. myset["key"] = true. However, I need the keys to be objects. I've read that Javascript casts property names to strings, so I guess I can't use myset[myobject] = true.
I could use an array, but I need something better than O(n) performance for adding, finding and removing items.
It needs to be able to tell objects apart by reference only, so given:
var a = {};
var b = {};
then both a and b should be able to be added, because they're separate objects.
Basically, I'm after something like C++'s std::set, that can store Javascript objects. Any ideas?
ES6 provides a native Set:
let s = new Set();
let a = {};
let b = {};
s.add(a);
console.log(s.has(a)); // true
console.log(s.has(b)); // false
Here's a mad suggestion ... key it on the result of JSON.stringify(object)
It's not possible for all objects, but if your object has a .toString() method implemented, it is:
var x = {toString: function(){ return 'foo'; }};
var y = {toString: function(){ return 'bar'; }};
var obj = {};
obj[x] = 'X';
obj[y] = 'Y';
console.log(obj);
// { foo: 'X', bar: 'Y' }
If you want to make this easier, make it a class:
function myObj(name){
this.name = name;
}
myObj.prototype.toString = function(){ return this.name; }
var obj = {};
obj[new myObj('foo')] = 'X';
obj[new myObj('bar')] = 'Y';
I'm answering my own question, but I came up with an alternative solution I thought was interesting and thought it would be useful to share it.
cwolves' answer gave me an idea. Providing an object's toString() method uniquely identifies the instance, properties of an object can be used to store a set of objects. Essentially, to store object x, you can use items[x.toString()] = x;. Note that the value is the object itself, so then the set of objects can be extracted by looking at all item's properties and dumping all the values in to an array.
Here's the class, which I call ObjectSet, in full. It requires objects are uniquely identified by their toString() method, which is OK for my purposes. add, remove and contains should all run in better than O(n) time - whatever javascript's property access efficiency is, which hopefully is either O(1) or O(n log n).
// Set of objects. Requires a .toString() overload to distinguish objects.
var ObjectSet = function ()
{
this.items = {};
this.item_count = 0;
};
ObjectSet.prototype.contains = function (x)
{
return this.items.hasOwnProperty(x.toString());
};
ObjectSet.prototype.add = function (x)
{
if (!this.contains(x))
{
this.items[x.toString()] = x;
this.item_count++;
}
return this;
};
ObjectSet.prototype.remove = function (x)
{
if (this.contains(x))
{
delete this.items[x.toString()];
this.item_count--;
}
return this;
};
ObjectSet.prototype.clear = function ()
{
this.items = {};
this.item_count = 0;
return this;
};
ObjectSet.prototype.isEmpty = function ()
{
return this.item_count === 0;
};
ObjectSet.prototype.count = function ()
{
return this.item_count;
};
ObjectSet.prototype.values = function ()
{
var i, ret = [];
for (i in this.items)
{
if (this.items.hasOwnProperty(i))
ret.push(this.items[i]);
}
return ret;
};
I used Map, solved my case
const objectsMap = new Map();
const placesName = [
{ place: "here", name: "stuff" },
{ place: "there", name: "morestuff" },
{ place: "there", name: "morestuff" },
];
placesName.forEach((object) => {
objectsMap.set(object.place, object);
});
console.log(objectsMap);
For what you're trying to do (sets of objects), there is no native Javascript implementation. You would have to implement this on your own. One way to do this would be to implement a hashing function for your objects. The backing data-type of the set would be an associative array, where the key of the array is the value you get from calling the object's hash function, and the value of the array is the object itself.
Of course, this doesn't address the issue that you highlighted, so you will need to take equality into account as well (implement an equals function perhaps)?
Instead of making the hash function a property of the object itself, you can have a standalone hash function that takes in an object as input and generates a hash value (presumably by iterating over its properties).
Using this method you should be able to get O(1) for insertion, searching, and removing (not counting the order of the hash function, which shouldn't be any worse than O(n), especially if you are iterating over its properties to create your hashed value).
ECMAScript6 Set should behave like that:
Standard: http://www.ecma-international.org/ecma-262/6.0/#sec-set-o-p-v-throw
Unofficial ES6 cheat sheet: https://github.com/lukehoban/es6features#map--set--weakmap--weakset
Working example on Firefox 32 (but not implemented in Chromium 37):
if (Set) {
var s = new Set()
var a = {}
var b = {}
var c = {}
s.add(a)
s.add(b)
s.add(b)
assert(s.size === 2)
assert(s.has(a))
assert(s.has(b))
assert(!s.has(c))
}
This is not surprising since {} != {}: equality compares object addresses by default.
A module that implements it for browsers without support: https://github.com/medikoo/es6-set
Javascript Set's don't do deep object comparison.
Using lodash, this is a unique array with deep object comparison:
const objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 2 }];
_.uniqWith(objects, _.isEqual);
Just typed this up, it's only briefly tested:
var Set = function Set()
{
var list = [];
var contains;
this.contains = contains = function(x) {
return list.indexOf(x) >= 0;
}
var put;
this.put = put = function(x) {
if (!contains(x))
list.push(x);
return this;
}
var remove;
this.remove = remove = function(x)
{
var idx = list.indexOf(x);
if (idx >= 0)
list.splice(idx,1);
return this;
}
var all;
this.all = all = function()
{
return list.concat();
}
return this;
}
It seems that the inner call of function works when prefixed with this.
Exemple:
var put;
this.put = put = function(x) {
if (!this.contains(x))
list.push(x);
return this;
}
Please use this code as a reference.
const fruits = [
{name: 'apple', price: 100},
{name: 'apple', price: 100},
{name: 'orange', price: 200},
{name: 'grapes', price: 300}
];
const hasFruitDuplicated = () => {
const duplicatedDeleteFruits = fruits.filter((fruit, index) =>
fruits.findIndex(item => item.name === fruit.name && item.price === fruit.price) === index
);
return duplicatedDeleteFruits;
};
Given an array of the following type:
Array<{ foo: T1, bar: T2 }>
You can build a corresponding dictionary of type:
{ [foo: T1]: Set<T2> }
The look-up for { foo: fooValue, bar: barValue } can be performed as follows:
if (fooValue in dictionary && dictionary[fooValue].has(barValue))
This way we can build what would be an ObjectSet<T1, T2>
.
If you now have three elements, you can build the following dictionary:
{ [foo: T1]: ObjectSet<T2, T3> }
and extend your ObjectSet to any number of properties by induction.
That is assuming your types can be used as index signatures.

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