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Remove duplicate index value from first array, manipulate second as per first(at some specific conditions)

This is the tricky one :
please understand my scenario:
I have two array , both array will have equal length always.
I want remove duplicate value in first array and second array will be manipulated according first one.
like if i have array like :
var firstArr = [1,1,4,1,4,5]
var secArr = ['sagar', 'vilas', 'suraj', 'ganesh','more','abhi']
//I want below Output
//[1,4,5] // this is firstArr after manipulation
//['sagar|vilas|ganesh','suraj|more',abhi] // this is secArr after manipulation
// here all duplicate values will be removed from first array
// and at same index second array will be manipulated.
please check my fiddle:
https://jsfiddle.net/abhilash503001/du4fe8ob/86/

You can use Map and reduce
First loop through the first array and map it values as key and take the values from second array's respective index as key
Now you have loop on the map's entries take the key's will be your unique firstArr and to get desired value for second arr you need to join values by |
var firstArray = [1,1,4,1,4,5]
var secArr = ['sagar', 'vilas', 'suraj', 'ganesh','more','abhi']
let op = firstArray.reduce((op,inp,index) => {
if(op.has(inp)){
let val = op.get(inp)
val.push(secArr[index])
op.set(inp, val)
} else {
op.set(inp,[secArr[index]])
}
return op
},new Map())
let {firstArr, secondArr} = [...op.entries()].reduce((op,[first,second])=>{
op.firstArr.push(first)
op.secondArr.push(second.join('|'))
return op
},{firstArr:[],secondArr:[]})
console.log(firstArr)
console.log(secondArr)

This is how I did it.
You first group the texts into arrays and then join them together.
var index_array = [1,1,4,1,4,5]
var text_array = ['sagar', 'vilas', 'suraj', 'ganesh','more','abhi'];
var manipulated_text_array = [];
var manipulated_index_array = [];
var groups = {};
for (let index in index_array) {
if (groups[index_array[index]] == undefined) {
groups[index_array[index]] = [];
}
groups[index_array[index]].push(text_array[index]);
}
for (let index in groups) {
manipulated_text_array.push(groups[index].join("|"));
}
manipulated_index_array = Object.keys(groups).map(x => parseInt(x));
console.log("texts", manipulated_text_array);
console.log("indexes", manipulated_index_array);

extract data of interest from array object

i am trying to extract specific data from an array object using keys but all the data gets returned? why is that? i want to print to the console all the values corresponding to the key genestart only
for (var i=0; i<genedata.matches.length;i++){
var arr = genedata.matches[i];
for (var key in arr){
var attrName=key;
var attrValue = arr[key];
//console.log(attrValue);
if (attrName='genestart'){
console.log(attrValue);
}
}
}

Your if statement is not a comparison but an assignment. Change = to ==

checking if more elements of array have same value of key , if they have remove one?

so I've tried everything that i know. Using map and filter, prototypes. Didn't work. .
[{"color":"black","type":"bmw"},{"color":"gray","type":"golf"}, {"color":"red","type":"bmw"}, {"color":"black","type":"mercedes"}]
So what I want to achieve, is when i do ajax, with javascript, to check if two or more object have same value for type, if there is for example two or more bmw-s, remove others and and push just one object with bmw type. Hope i am clear enough.
Thanks in advance

function removeDuplicates(arr) {
var alreadyExist = {}; // hash object to keep track of elemnt that have already been encountered
var indexes = []; // array of indexes that will be removed
arr.forEach(function(o, i) { // for each object o in arr
if(alreadyExist[o.type]) // if the type of the object o at index i already exist
indexes.push(i); // mark its index i to be removed later
else // if not
alreadyExist[o.type] = true; // then mark the object as found so other ones will be removed
});
// for each index in the indexes array
for(var i = 0; i < indexes.length; i++)
arr.splice(indexes[i] - i, 1); // remove the object at that index ( - i because the array arr is continually changing. Its length decrease every time we remove an item)
}
var array = [{"color":"black","type":"bmw"},{"color":"gray","type":"golf"}, {"color":"red","type":"bmw"}, {"color":"red","type":"bmw"}, {"color":"red","type":"bmw"}, {"color":"black","type":"mercedes"}];
removeDuplicates(array);
console.log(array);

don't remove elements, create a filtered Array:
var yourArray = [{"color":"black","type":"bmw"},{"color":"gray","type":"golf"}, {"color":"red","type":"bmw"}, {"color":"black","type":"mercedes"}];
var cache = {},
filteredArray = yourArray.filter(({type}) => type in cache? false: (cache[type] = true));
console.log(filteredArray);
It's non destructive, more performant and even simpler and shorter.
Edit: And even without modern features:
var filteredArray = yourArray.filter(function(item){
return item.type in this? false: (this[item.type] = true);
}, {/* the cache-object */}); //abusing `this` to pass the cache object

You can keep track of which types are already present in your array with an object, then only push into new array those that are not present:
var vehicles = [{"color":"black","type":"bmw"},{"color":"gray","type":"golf"}, {"color":"red","type":"bmw"}, {"color":"black","type":"mercedes"}];
var uniques = [];
var types = {};
for (var i = 0; i < a.length; i++) {
if (!types[a[i].type]) { uniques.push(a[i]); }
types[a[i].type] = true;
}
//uniques = [{"color":"black","type":"bmw"},{"color":"gray","type":"golf"}, {"color":"black","type":"mercedes"}];

How to set hash key dynamically in javascript

With this code,
h = {}
for (var i in [0,1]){ h[i.ToString] = i; }
I expected same result with h["1"] = 1 and h["2"] = 2.
Why is this code doesn't work, and how can I define hash key dynamically in javascript?

The for .. in loop in JS iterates over keys, not over values (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in).
So in your case, you iterate over the keys of the array you have in there.
Those will be 0, 1, 2 ... no matter what you put in there.
What you could do instead would be something like this:
var obj = {};
var data = [1,2,3,4];
data.forEach(function(val) {
obj[val] = val;
});

Can't reference array by index

I have an array defined as:
var subjectCache = [];
I then have some code to build it up, which is working ok.
However, if I try to reference the array by an index, e.g.:
var x = subjectCache[0];
or
var x = subjectCache[1];
I get undefined.
Also subjectCache.length is always 0 (zero).
if I try to reference it by its key, e.g.:
var x = subjectCache['12345'];
it works.
Is this normal? Shouldn't I be able to reference it by its index whatever?
I'm using Internet Explorer, if it makes a difference (and it probably does :( )
[Edit]
this is the code I'm using to build the array, although I really don't think it is to blame.
It's a callback from a webservice call. This is working fine and the array is being populated.
var subjectCache = [];
var subjectCacheCount = 0;
function refreshSubjectsCallback(data) {
// update subjects
// loop through retrieved subjects and add to cache
for( i=0; i < data.length; i++ )
{
var subject = data[i];
var subjectid = subject.SubjectId;
subjectCache[subjectid] = subject;
subjectCacheCount += 1;
}
}
[/Edit]

You're probably assigning keys manually instead of using subjectCache.push() to add new elements to the array:
var array = [];
array['foo'] = 'bar';
console.log(array.length); // 0
The length attribute isn't going to reflect those changes the way you'd expect:
> var a = [];
undefined
> a[100] = 2; // The previous `100` entries evaluate to `undefined`
2
> a.length;
101
Instead, use an object:
var object = {};
object['foo'] = 'bar';
for (var key in object) {
var value = object[key];
console.log(value);
}

From your symptoms, it sounds like you are trying to treat the array as an associative array.
In Javascript, arrays work like this:
var a = [];
a[1] = 10;
alert(a.length);
Objects work like this:
var o = {};
o.myProp = true;
o["myOtherProp"] = false;

Arrays only work with numeric keys not strings. Strings assign properties to the object, and aren't counted as part of length nor it's numeric indices.
When building the array, make sure you are assigning to a numeric position within the array.

No, it will not work, because you haven't created arrays but objects.
you will have to access it by its key.
var x = subjectCache['12345'];
If this works and subjectCache.length doesn't, I think you are making an object not an array. You are confused.

Somewhere along the road you lost the array, and the variable subjectCache points to a different kind of object.
If it was an array, it can't have the length zero and contain an item that is reachable using subjectCache['12345']. When you access an item in an array it doesn't make any difference if you use a numeric index or a string representing a number.