I have an array A containing n arrays. Each of the n arrays, contains two element. The first is an id, while the second is an object. For more details, see the following example:
A = [ [100, object1], [22, object2], [300, object3]]
For a given id, I want to get the associated object. Example, for id = 22, I want to get object2.
Loop, check, and return
function getById(id) {
for (var i = 0; i < A.length; i++) {
if (A[i][0] == id) {
return A[i][1];
}
}
return false;
}
CoffeescriptThis is a very basic way of doing it. Iterate over A, keep checking whether the first member of each array matches your id, and return the associated object in case of a match.
function returnObjectById(id) {
for (var i=0; i< A.length; i++) {
if (A[i][0]==id) {
return A[i][1];
}
}
return false; // in case id does not exist
}
In Coffeescript:
returnObjectById = (id) ->
i = 0
while i < A.length
if A[i][0] == id
return A[i][1]
i++
false
# in case id does not exist
A CoffeeScript version could like:
find_in = (a, v) ->
return e[1] for e in a when e[0] == v
then you could say:
thing = find_in(A, 22)
You'd get undefined if there was no v to be found.
The for e in a is a basic for-loop and then when clause only executes the body when its condition is true. So that loop is functionally equivalent to:
for e in a
if e[0] == v
return e[1]
The fine manual covers all this.
return e[1] for e in a when e[0] == v ? Thanks
for e in array is not the same as JavaScript's, JavaScript's in loop would be for k of object in CoffeeScript.In CoffeeScript you can use the JS to CF transition
getById = (id) ->
i = 0
while i < A.length
if A[i][0] == id
return A[i][1]
i++
false
