Is there an easy way to replace all appearances of an primitive in an array with another one. So that ['a', 'b', 'a', 'c'] would become ['x', 'b', 'x', 'c'] when replacing a with x. I'm aware that this can be done with a map function, but I wonder if have overlooked a simpler way.
5 Answers
In the specific case of strings your example has, you can do it natively with:
myArr.join(",").replace(/a/g,"x").split(",");
Where "," is some string that doesn't appear in the array.
That said, I don't see the issue with a _.map - it sounds like the better approach since this is in fact what you're doing. You're mapping the array to itself with the value replaced.
_.map(myArr,function(el){
return (el==='a') ? 'x' : el;
})
answered Nov 8, 2013 at 13:21
Benjamin Gruenbaum
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3 Comments
Andreas Köberle
The question was about primitives not just strings. Also I want to use lodash, as this will be one step in a longer chain, where the array data is manipulated in.
Benjamin Gruenbaum
@AndreasKöberle First of all using a particular library is a mean and not a goal. Second of all - in that case
_.map is what you're looking for, underscore/lodash has no specific replace/swap functionality on collections, you can add it to the lodash prototype yourself if you'd like.
Denys Séguret
_.map is really fit to this use case, there's no need to look for anything else.
I don't know about "simpler", but you can make it reusable
function swap(ref, replacement, input) {
return (ref === input) ? replacement : input;
}
var a = ['a', 'b', 'a', 'c'];
_.map(a, _.partial(swap, 'a', 'x'));
Comments
If the array contains mutable objects, It's straightforward with lodash's find function.
var arr = [{'a':'a'}, {'b':'b'},{'a':'a'},{'c':'c'}];
while(_.find(arr, {'a':'a'})){
(_.find(arr, {'a':'a'})).a = 'x';
}
console.log(arr); // [{'a':'x'}, {'b':'b'},{'a':'x'},{'c':'c'}]
Comments
Another simple solution. Works well with arrays of strings, replaces all the occurrences, reads well.
var arr1 = ['a', 'b', 'a', 'c'];
var arr2 = _.map(arr1, _.partial(_.replace, _, 'a', 'd'));
console.log(arr2); // ["d", "b", "d", "c"]
Comments
A replace method like this one could work:
const replacer = (contextArray, itemToReplace, replaceWith) => _.map(
contextArray,
(n) => n === itemToReplace ? replaceWith : n
)
console.log(replacer(['a', 'b', 'a', 'c'], "a", "x"))<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.19/lodash.min.js"></script>
map()in this case? It's the perfect tool for the job._(array).filter('someKey').replace('a', 'x')looks very natural to me