My goal is to push an array into another array. However the array will not be pushed if the value within a[1] exists from a previous push.
simplified example of my attempt
curated_array = [];
for(i =0; i < 4; i++) {
console.log(i);
if(i ==0){
a = ['John','15799','United States'];
}
else if(i ==1){
a = ['Tim','86037','United States'];
}
else if(i==2){
a = ['George','15799','Great Britain'];
}
else if(i ==3){
a = ['Lucas','26482','Greece'];
}
else if(i ==4){
a = ['Joshua','83620','United States'];
}
curated_array = curated_array.filter(f => f!= a).concat([a]);
}
console.log(curated_array);
Actual outcome
[ [ 'John', '15799', 'United States' ],
[ 'Tim', '86037', 'United States' ],
[ 'George', '15799', 'Great Britain' ],
[ 'Lucas', '26482', 'Greece' ],
[ 'Joshua', '83620', 'United States' ] ]
Desired outcome -- to remove the row where a[1] = 15799, since it has happened already
[ [ 'John', '15799', 'United States' ],
[ 'Tim', '86037', 'United States' ],
[ 'Lucas', '26482', 'Greece' ],
[ 'Joshua', '83620', 'United States' ] ]
While @Barmar's comment makes your code work, it's inefficient to iterate over the whole array every time to check if you've seen the value before.
Please consider using a different data structure such as a Set or key-val pairs:
Answer with key-val pairs/hash map-like:
inputs = [ [ 'John', '15799', 'United States' ],
[ 'Tim', '86037', 'United States' ],
[ 'George', '15799', 'Great Britain' ],
[ 'Lucas', '26482', 'Greece' ],
[ 'Joshua', '83620', 'United States' ] ]
// build a hash map, O(n) => you only need to build this once
uniqueInputs = {}
inputs.forEach(input => {
valueToCheck = input[1]
// checking for a key in an object is O(1)
if (! (valueToCheck in uniqueInputs) )
uniqueInputs[ valueToCheck ] = input
})
// turn the object back into an array
output = Object.values( uniqueInputs )
Output:
[
[
"John",
"15799",
"United States"
],
[
"Lucas",
"26482",
"Greece"
],
[
"Joshua",
"83620",
"United States"
],
[
"Tim",
"86037",
"United States"
]
]