A regex will work.

const rx = /\s+:.*$/mg
str.replace(rx, '')

https://regex101.com/r/sV2TnQ/1

The g flag will replace multiple occurances. The m flag lets $ match end of line or document.

So 'spaces', a 'colon', and 'all to end of line'

try like this,

const str = 'accept : menerima'

console.log(str.slice(0,str.indexOf(":")))

You can create one method, which will take string as input and will return new string.

const txt = 'accept : menerima'

function getCroppedString(str){
    return str.slice(0,str.indexOf(":"));
}

getCroppedString(txt)

console.log(getCroppedString(txt));

const str = 'accept : menerima'

console.log(str.slice(0,str.indexOf(":")))

A different approach to a regex would be to loop over the lines, and split the : using a map.

const string = `accept : menerima
accuse : menuduh 
achieve : mencapai 
acquire : memperoleh 
adapt : menyesuaikan 
add : menambahkan`;

const lines = string.split("\n")
.map((line) => line.split(" : ")[0])

// Optionally if you would like to return the output as a single string
.join("\n"); 

console.log(lines);