I have a array for store object, which have an object in it already:
var obj = [{
name: 'json',
lang: 'en'
}];
console,.log(obj) //the result is OK;
then I want push another object into it, just like:
var newObj = {
name: 'lee',
lang: 'zh'
}
obj.push(newObj)
but after this I print the obj array,console.log(obj), the result is 2 !!
Why this happen? How can I solve this problem?To store object in array correctly
Make sure you didn't do obj = obj.push(newObj);, because .push method returns the number of elements after push; instead, the line should simply read obj.push(newObj).
Related
I want to access a specific property in an object. Using an array for example
let array = ["tom","tony", "jerry"];
let object = {
tony: "Brother",
tom: "Uncle",
jerry: "Cousin",
};
object.array[1];
I'm trying to access object.tony but what happens is that it returns object."tony" instead.
The problem is that it returns it as a string so it causes an error.
Is it possible to return array[1] not as a string?
In object.array[1], JS will think your looking for array inside object, which does not exist. If an array was in the object, it would work:
let object = {
array: ["tom", "tony", "jerry"],
// some other stuff...
};
console.log(object.array[1]);
You can use brackets instead:
object[array[1]];
Example:
let array = ["tom","tony", "jerry"];
let object = { tony: "Brother", tom: "Uncle", jerry: "Cousin", };
console.log(object[array[1]]);
I have data for example like this:
data: [{
tag: 'Apple',
}, {
tag: 'Microsoft',
}, {
tag: 'Google',
}]
And I want to convert them into like this:
data: ['Apple','Microsoft','Google']
Is there a best way to do this? Wherever I am reading, people are using complex logic using loops. So are there alternative methods to doing this?
One way is to use Array.map and replace the object ele.tag with just the value return ele.tag:
var data =
[{
tag: 'Apple',
}, {
tag: 'Microsoft',
}, {
tag: 'Google',
}];
data = data.map(function(ele){ return ele.tag; });
console.log(data);
Or in ES6 you can simply this even more:
data = data.map(ele => ele.tag);
You could use a for-in loop and push the attribute of the object into an array.
var data = [{
tag: 'Apple',
}, {
tag: 'Microsoft',
}, {
tag: 'Google',
}];
var tags = [];
for (prop in data) {
tags.push(data[prop].tag);
}
console.log(tags);
For easier handling let's take the object in the OP's code and assign it to a variable, as follows:
var obj = {"data":[{"tag":'Apple'},{"tag":'Microsoft'},{"tag":'Google'}]};
var {data}= obj; // object destructing ...
var mapped = data.map(function( e ){ return e.tag});
// re-assigning value of object's data property
obj["data"] = mapped;
console.log(obj); // obj.data now pertains to array of strings
The problem described by the OP involves an object whose data property refers to an array of objects, each with a tag property. The OP inquires as to how to revise the data property so that it refers instead to an array of string values corresponding to each object's tag property.
This example makes use of destructuring to access the array of objects. Then, it uses the array's map() method to access every element's tag property and thereby obtain its string value. The beauty of map() is that it performs iteration behind the scenes sparing the user from having to hand-code a loop with the correct logic -- although in functional programming languages instead of using iteration, recursion is more apt to be utilized for this purpose. Finally, the value of the object's data property is reset to contain the specified array of strings.
I'm getting output: [{"ref":"contact.html","score":0.7071067811865475}]
$.getJSON( "index.json", function(content) {
idx = lunr.Index.load(content);
var results = idx.search(variabletosearch);
var final = JSON.stringify(results);
console.log(final);
});
How can I print value of ref? When I console.log(final[0].ref); I get undefined.
EDIT:
JSON.stringify returns a string, not an object. So in this case 'final' is a string that contains the same data that was in the object 'results'
To access the data from an object, you can use result[0].ref, or if you want to use 'final' (although you don't need to), you can do this:
final = JSON.parse(final)
console.log(final[0].ref)
If it's only one object within the array, then the other answers are enough, but since arrays are used to store multiple objects, you can do this as follows:
var arr = [
{"ref": "object1", "score": "1"},
{"ref": "object2", "score": "2"}
]
arr.map(function(object) {
console.log(object.ref)
})
JSFiddle using an alert instead of console.log()
You can also use a loop, but this cleaner.
var a = [{"ref":"contact.html","score":0.7071067811865475}];
a[0].ref;
a[0] is the '0'th (or first) element in the array which is the object literal {"ref":"contact.html","score":0.7071067811865475} from here you can access the object normally using dot notation.
Expanded out a bit:
var a = [{"ref":"contact.html","score":0.7071067811865475}];
var myObject = a[0];
console.log(myObject.ref);
//or with null checking
if (myObject) {
console.log(myObject.ref ? myObject.ref : 'no value');
}
Well, assuming
var myvar = [{"ref":"contact.html","score":0.7071067811865475}];
then:
var myref = myvar[0].ref;
I have an object:
var Obj = [{
id: "",
position: {
cartesian: [],
polar: [],
bob: "INERTIAL"
}
}];
When I go to set obt.id
Obj.id="sam/reconnaissance - "+samName;
It works fine.
However when I go to access Obj.position.cartesian
(Obj.position.cartesian).push(fooBar[i][t][p]);
I get this error:
(Obj.position.cartesian).push(fooBar[i][t][p]);
^
TypeError: Cannot read property 'cartesian' of undefined
Why? I have tried Obj['position']['cartesian'] and still nothing
What am I doing wrong?
Obj is not an object, it is an Array so you have to access first element with index 0. Try it like
Obj[0]['position']['cartesian']
You aren't using an object, you are using an array.
An object looks like this:
var obj = {
id: 0
};
What you have is an object within an array: (note [)
var obj = [{id: 0}];
Obj is an array with single element as object, hence to access position you can use any of these syntax
Obj[0]['position']['cartesian']
Obj[0].position.cartesian
Again cartesian is an array hence to call push you can use
Obj[0]['position']['cartesian'].push(foobar[i][t][p])
Obj[0].position.cartesian.push(foobar[i][t][p])
I need to group item having same name property and increase their number. I try to assign to new array and check existed item by key. It works fine when I use this solution in PHP, but in JavaScript it doesn't.
I have searched some similar questions, but I don't know why it doesn't work.
var orgArr = [
{name: 'abc', number: 3},
{name: 'xyz', number: 2},
{name: 'abc', number: 5}
];
var result = []; //work if result = {};
for (var i = 0; i < orgArr.length; i++) {
if (!result[orgArr[i].name]) {
result[orgArr[i].name] = orgArr[i]; //assign new
} else {
result[orgArr[i].name].number += orgArr[i].number; //increase number if name exist in result array
}
}
alert(JSON.stringify(result)); //expect array 2 item but it's empty array
console.log(result); //Will have result 2 item when I view console window
var orgArr = [
{name: 'abc', number: 3},
{name: 'xyz', number: 2},
{name: 'abc', number: 5}
];
var result = []; //work if result = {};
var tempArray = []; // used to store unique name to prevent complex loop
orgArr.forEach(function(item){
if($.inArray(item.name, tempArray)< 0){// unique name
result.push(item);
tempArray.push(item.name);
}
else{
var indexNew = $.inArray(item.name, tempArray);
result[indexNew].number += item.number;
}
});
alert(JSON.stringify(result)); //expect array 2 item but it's empty array
console.log(result); //Will have result 2 item when I view console window
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
E/ My previous answer was incorrect.
Well.. yes...
[] designates an array. An array holds everything by integer values. You're trying to feed it a string value (orgArr[x].name) and since its just an array, it discards it as a bad call.
{} is an object. Objects can have string indexes.
var result = []; //work if result = {};
Why can't result be {}?
if you want it to work, make result = {} not []
an array is not a key value store. It still will take key values, and will store them on the array object. But when stringify encounters your array, it determines it is an array and then trys to iterate the array, and your array appears empty. so you get nothing in your output.
You get empty array it's because by default JSON.stringify failed to convert your array to json string.
By default JSON.stringify converts int-based index array to json string but you are using orgArr[i].name which is a string as array index that the cause alert() show empty array.
Can you explain why would you want to convert json array to an array with string index. It's always better to use json array if you want a string as key/index.
For more information about JSON.stringify