In general it's a bad practice to mutate the input. In some katas it doesn't make a problem, but it does in others. If you have weird/ununderstandable results it's something to check out prioritarily.

Not a kata issue. You passed the kata, so you must be doing something else wrong.

Thanks I found what i was doing wrong here.

Some tests are susceptible to mutation of input arguments and fail if your solution changes input objects passed to it. If the kata does not explicitly ask you to modify input arguments, make sure you do not do it. If you find a kata that fails when input is mutated by your solution, raise it as an issue (see here).

An error message, as it says, due to a syntax error, the compiler/interpreter finds the end of code while it should not. Most probably a bug in your code. Always say which language you're using (I guess JavaScript).

what is this below ?

/workspace/node/test.js:30

SyntaxError: Unexpected end of input
at wrapSafe (internal/modules/cjs/loader.js:915:16)
at Module._compile (internal/modules/cjs/loader.js:963:27)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)
at Module.load (internal/modules/cjs/loader.js:863:32)
at Function.Module._load (internal/modules/cjs/loader.js:708:14)
at Module.require (internal/modules/cjs/loader.js:887:19)
at require (internal/modules/cjs/helpers.js:74:18)
at Object.exports.requireOrImport (/workspace/node/node_modules/.pnpm/mocha@8.3.0/node_modules/mocha/lib/esm-utils.js:42:12)
at Object.exports.loadFilesAsync (/workspace/node/node_modules/.pnpm/mocha@8.3.0/node_modules/mocha/lib/esm-utils.js:55:34)
at Mocha.loadFilesAsync (/workspace/node/node_modules/.pnpm/mocha@8.3.0/node_modules/mocha/lib/mocha.js:431:19)
at singleRun (/workspace/node/node_modules/.pnpm/mocha@8.3.0/node_modules/mocha/lib/cli/run-helpers.js:125:15)
at exports.runMocha (/workspace/node/node_modules/.pnpm/mocha@8.3.0/node_modules/mocha/lib/cli/run-helpers.js:190:10)
at Object.exports.handler (/workspace/node/node_modules/.pnpm/mocha@8.3.0/node_modules/mocha/lib/cli/run.js:362:11)
at /workspace/node/node_modules/.pnpm/yargs@16.2.0/node_modules/yargs/build/index.cjs:443:71

First, read this: https://docs.codewars.com/training/troubleshooting/

About your problem: your function is returning 'There will be no Python developers' if the first developer's language isn't Python.

its not workignwith javascript or my mistake