Search jQuery

jQuery Forum

Getting Started

raviojo

Find count of occurrences of a key in an array that appears only once?

in Getting Started • 4 years ago

i have the following array

test ={ [id:1,subject:math], [id:2,subject:math], [id:1,subject:science], [id:3,subject:science], }

how can I find the key that appears only once like.. [id:2,subject:math] , [id:3,subject:science].

I need to output the key id value 2 and 3.

Thank you

Replies(12)

watusiware

Re: Find count of occurrences of a key in an array that appears only once?

4 years ago

Start with some valid Javascript. What you have above is not.

Arrays don't have keys. And objects MUST have keys.

What do you really have? Is this just a copy/paste error? Did you put { where you meant [ and [ where you meant {?

As well, your values have to be quoted, unless you actually have VARIABLES named math and science.

Open up your browser's console window and always check for errors.

And normally you should declare variables with var (or let or const if you use ES6). Did you actually mean test to be a global variable, or did you forget to declare it? It's best to be explicit about globals, and if you meant it to be global write window.test = (globals in browser Javascript are really just properties of the window object.)

raviojo

Re: Find count of occurrences of a key in an array that appears only once?

4 years ago

Hi watusiware,

yes..it was a typo..

this is how it looks.. its dynamically created.

test =[ [id:1,subject:math], [id:2,subject:math], [id:1,subject:science]]

Thank you

watusiware

Re: Find count of occurrences of a key in an array that appears only once?

4 years ago

That still is not valid Javascript.

Open up your browser console, and check for errors!

Use a linter plugin or for your code editor, or use a code editor that already has a linter built-in.

Do you mean to have an array of objects?

Are math and science meant to be strings, or the names of variables you have already defined?

watusiware

Re: Find count of occurrences of a key in an array that appears only once?

4 years ago

If you mean to have an array of objects, and math and science are meant to be strings;

var test =[ {id:1,subject:'math'},{id:2,subject:'math'}, {id:1,subject:'science'} ]

console.log(test); // show your array of objects on console

watusiware

Re: Find count of occurrences of a key in an array that appears only once?

4 years ago

Sorry, I edited that several times. Refresh your browser window.

jakecigar

Re: Find count of occurrences of a key in an array that appears only once?

4 years ago

Look at the fiddle I wrote for you in your last question. It’s properly defined!

JΛ̊KE

raviojo

Re: Find count of occurrences of a key in an array that appears only once?

4 years ago

Hi watusiware,

This is how i create the array:

test.push({ id: attrValue, subject: inputValue }) in for loop...hence i posted the example array by typing it . you are correct below is the correct format.

var test =[ {id:1,subject:'math'},{id:2,subject:'math'}, {id:1,subject:'science'} ]

Can you please tell how i can find which id is present only once?

watusiware

Re: Find count of occurrences of a key in an array that appears only once?

4 years ago

Your question doesn't make sense.

Do you want to find the ids (plural) that are only present once? There could be more than one.

raviojo

Re: Find count of occurrences of a key in an array that appears only once?

4 years ago

var test =[ {id:1,subject:'math'},{id:2,subject:'math'}, {id:1,subject:'science'} ]

in above example id:1 has both math and science subjects where id:2 has only math(1 subject).. i would like to return the number 2 and store it a variable.

Thank you

watusiware