This question already has answers here:
Pick random property from a Javascript object
(9 answers)
Get array of object's keys
(8 answers)
Closed 2 years ago.
I have a Javascript hash of Spanish words/phrases and their English meanings:
let phrases = {
hola: "hello",
adios: "bye",
};
I want to select a random key. I have tried for a while, and my latest attempt hasn't worked and returns undefined:
var keys = phrases.keys;
var len = phrases.length;
var rnd = Math.floor(Math.random()*len);
var key = phrases[rnd];
I've looked at other Stack Overflow answers but can't seem to find exactly what I'm looking for. Any ideas please?
Probably you can use Object.keys() instead.
Try the following:
const phrases = {
hola: "hello",
adios: "bye",
};
const keys = Object.keys(phrases);
const len = keys.length;
const rnd = Math.floor(Math.random() * len);
const key = phrases[keys[rnd]];
console.log(key);
I hope this helps!
Related
This question already has answers here:
How to use a variable for a key in a JavaScript object literal?
(16 answers)
Is it possible to add dynamically named properties to JavaScript object?
(20 answers)
Closed 2 years ago.
I'm trying to find out how to initialise an array of objects, where each object has the index (i) as its key and 0 as its value. The code below is not working as expected but I can't see why. I'm still quite beginner with Javascript and couldn't find an answer elsewhere.
var n = 10;
var sample = [];
for (var i = 0; i < n; i++)
sample.push({i : 0});
you should use this syntax sample.push({[i]: 0});
when you need to access object property which is stored under some variable you should always use square brackets no matter you need write to or read from an object
The code below should take care of the job:
let n = 10;
let sample = Array.from({length:n}, (_, i) => ({ [i]: 0 }));
As pointed by Oleksandr Sakun on his answer, the index is used between brackets in order to evaluate the variable and set as a property of the object.
For a funcitonal approach you can try:
const initArray = (n)=>{
const newArr = new Array(n).fill(0);
return newArr.map((value, index)=> ({[index]: value}))
}
add square brackets to the index [i] :
var n = 10;
var sample = [];
for (var i = 0; i < n; i++)
sample.push({[i]: 0});
console.log(sample);
This question already has answers here:
Javascript Property with three dots (...)
(5 answers)
What does this symbol mean in JavaScript?
(1 answer)
Closed 2 years ago.
I have gone through the following JavaScript code:
let num = [1,2,2,2,3,4,5];
console.log([... new Set(nums)]); //which prints [1,2,3,4,5]
I did not understand what this ... device (three dots) does in this example.
I think you need to read Iteration first;
let nums = [1,2,2,2,3,4,5];
let setFromArray = new Set(nums);
let arrayFromSet_spread = [...setFromArray];
console.log("spread", arrayFromSet_spread);
// here the spread will iterate over iteratable and return current value
//arrayFromSet can be written without spread like this
let arrayFromSet_forOf = [];
for ( let el of setFromArray ) {
arrayFromSet_forOf.push(el)
}
console.log("forOf",arrayFromSet_forOf);
// and the most naive way to iterate :)
let arrayFromSet_ManualIteration = [];
let setFromArrayIterator = setFromArray[Symbol.iterator]();
const firstElement = setFromArrayIterator.next();
const secondElement = setFromArrayIterator.next();
const thirdElement = setFromArrayIterator.next();
const fourthElement = setFromArrayIterator.next();
const fifthElement = setFromArrayIterator.next();
const sixthElement = setFromArrayIterator.next();
arrayFromSet_ManualIteration.push(firstElement);
arrayFromSet_ManualIteration.push(secondElement);
arrayFromSet_ManualIteration.push(thirdElement);
arrayFromSet_ManualIteration.push(fourthElement);
arrayFromSet_ManualIteration.push(fifthElement);
arrayFromSet_ManualIteration.push(sixthElement);
//you could just push values not the itaration object itself
//arrayFromSet_ManualIteration.push(firstElement.value);
//arrayFromSet_ManualIteration.push(secondElement.value);
//arrayFromSet_ManualIteration.push(thirdElement.value);
//arrayFromSet_ManualIteration.push(fourthElement.value);
//arrayFromSet_ManualIteration.push(fifthElement.value);
console.log('ManualIteration full objects',arrayFromSet_ManualIteration);
This question already has answers here:
Remove duplicate values from JS array [duplicate]
(54 answers)
Closed 6 years ago.
I am using above code and removing the items based on id
I am getting id is not defined while comparing i+1 item when i reaches to maximum array length.
Appreciate your help....
var arr = [{"id":"0-block-0","left":206.5,"top":0},{"id":"0-block-1","left":446.5,"top":0},{"id":"0-block-2","left":474.5,"top":16},{"id":"0-block-2","left":686.5,"top":0}];
Expecting outout = [{"id":"0-block-0","left":206.5,"top":0},{"id":"0-block-1","left":446.5,"top":0},{"id":"0-block-2","left":686.5,"top":0}]
Array.prototype.unique = function(){
var passNum = this.length;
var _self = this;
// to repeat loops n*n times
while(passNum>0){
for(var i = 0;i<this.length;i++) {
if(this[i].id==this[i+1].id){
var _indx = this.indexOf(this[i]);
this.splice(_indx,1);
}
}
passNum = passNum-1;
}
return this;
};
You can do this with ES2015 Sets.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set
EDIT: If you can't use ES2015, there is a polyfill available.
This question already has answers here:
How to get all properties values of a JavaScript Object (without knowing the keys)?
(25 answers)
Closed 9 years ago.
I have map/dictionary in Javascript:
var m = {
dog: "Pluto",
duck: "Donald"
};
I know how to get the keys with Object.keys(m), but how to get the values of the Object?
You just iterate over the keys and retrieve each value:
var values = [];
for (var key in m) {
values.push(m[key]);
}
// values == ["Pluto", "Donald"]
There is no similar function for that but you can use:
var v = Object.keys(m).map(function(key){
return m[key];
});
This question already has answers here:
Closed 11 years ago.
Possible Duplicates:
JavaScript: Getting random value from an array
How can I choose an object key at random?
suppose we have an array like this:
var MrArray = new Array(5);
MrArray['one']='oneValue';
MrArray['two']='twoValue';
MrArray['three']='threeValue';
MrArray['four']='fourValue';
MrArray['five']='fiveValue';
ok?
the Array is associated.
and we have string key and string value.
now! how can i pick a random value from that?
Edit:i want to use like this:
Array Key Here
Regards
Sam
Using the method described here we can create the following function:
function randomKey(obj) {
var ret;
var c = 0;
for (var key in obj)
if (Math.random() < 1/++c)
ret = key;
return ret;
}
It returns a random key, so to get a random value from MrArray, do this:
var value = MrArray[randomKey(MrArray)];
jsPerf benchmark comparing the speed of this and the other answer.
Here:
function fetch_random(obj) {
var temp_key, keys = [];
for(temp_key in obj) {
if(obj.hasOwnProperty(temp_key)) {
keys.push(temp_key);
}
}
return obj[keys[Math.floor(Math.random() * keys.length)]];
}
Src: How can I choose an object key at random?