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example we have this js array (some kind like lat, lng):
items = [
[aa,aa],
[bb,bb],
[cc,cc]
]
the result that i expected should be like this:
A = [
[aa,aa],
[bb,bb]
]
B = [
[bb,bb],
[cc,cc]
]
You are trying to iterate over two consecutive elements (arrays), you can use ruby_cons.
Note: This is a Ruby solution to iterate over consecutive elements.
items.each_cons(2) do |arr|
p arr
end
in javascript, you can try sth like,
> items
[ [ 42.32, 47.32 ], [ 49.434, 41.343 ], [ 43.34, 43.45 ] ]
> container = []
[]
> for(var i = 0; i<items.length-1; i++) {
... container.push(items.slice(i, i+2));
... }
2
> container[0]
[ [ 42.32, 47.32 ], [ 49.434, 41.343 ] ]
> container[1]
[ [ 49.434, 41.343 ], [ 43.34, 43.45 ] ]
more generalized solution, inspired from ruby's each_cons(n) enumerable method.
> each_cons = function(enm, cons_size) {
... var results = [];
... /*
... * checking numericality like typeof cons_size == 'number'
... * might be useful. but i'am skipping it.
... */
... cons_size = (cons_size < 1 ? 1 : cons_size );
... // setting default to 2 might be more reasonable
... for (var i=0; i<=enm.length - cons_size; i++) {
..... results.push(enm.slice(i, i+cons_size));
..... }
... return results;
... }
[Function: each_cons]
> x = [1,2,3,4,5,6,7,8,9,0];
[ 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 ]
> each_cons(x, 0)
[ [ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ], [ 6 ], [ 7 ], [ 8 ], [ 9 ], [ 0 ] ]
> each_cons(x, 1)
[ [ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ], [ 6 ], [ 7 ], [ 8 ], [ 9 ], [ 0 ] ]
> each_cons(x, 2)
[ [ 1, 2 ],
[ 2, 3 ],
[ 3, 4 ],
[ 4, 5 ],
[ 5, 6 ],
[ 6, 7 ],
[ 7, 8 ],
[ 8, 9 ],
[ 9, 0 ] ]
> each_cons(x, 3)
[ [ 1, 2, 3 ],
[ 2, 3, 4 ],
[ 3, 4, 5 ],
[ 4, 5, 6 ],
[ 5, 6, 7 ],
[ 6, 7, 8 ],
[ 7, 8, 9 ],
[ 8, 9, 0 ] ]
>
> x= "hippopotomonstrosesquipedaliophobia"; //https://en.wiktionary.org/wiki/hippopotomonstrosesquipedaliophobia
'hippopotomonstrosesquipedaliophobia'
> each_cons(x, 3)
[ 'hip',
'ipp',
'ppo',
'pop',
'opo',
'pot',
'oto',
'tom',
'omo',
'mon',
'ons',
'nst',
'str',
'tro',
'ros',
'ose',
'ses',
'esq',
'squ',
'qui',
'uip',
'ipe',
'ped',
'eda',
'dal',
'ali',
'lio',
'iop',
'oph',
'pho',
'hob',
'obi',
'bia' ]
>
> x = [[1,2], ['a', 'b'], [2,3,4, {a: 5}]]
[ [ 1, 2 ], [ 'a', 'b' ], [ 2, 3, 4, { a: 5 } ] ]
> each_cons(x, 2)
[ [ [ 1, 2 ], [ 'a', 'b' ] ],
[ [ 'a', 'b' ], [ 2, 3, 4, [Object] ] ] ]
Related
when I try to add the new element to the array it changes the rest of the elements by repeating the last one I added
I'm learning to program in java script and I found this error not because it occurs can someone explain it to me
input=`^>v<`
input=input.split("")
var coordinates=[0,0]
var positions=[]
y=0
v=0
for (x in input){
v+=1
x=input[x]
if (x=="^"){
coordinates[1]+=1
}
if (x=="v"){
coordinates[1]-=1
}
if (x==">"){
coordinates[0]+=1
}
if (x=="<"){
coordinates[0]-=1
}
boolean=positions.indexOf(coordinates)
positions.push(coordinates)
console.log(coordinates)
}
console.log(positions)
output
[ [ 0, 1 ] ]
[ [ 1, 1 ], [ 1, 1 ] ]
[ [ 1, 0 ], [ 1, 0 ], [ 1, 0 ] ]
[ [ 0, 0 ], [ 0, 0 ], [ 0, 0 ], [ 0, 0 ] ]
[ [ 0, 0 ], [ 0, 0 ], [ 0, 0 ], [ 0, 0 ] ]
The code in python is:
def trimTree(tree):
p=tree[1]
if type(p) == type(""): return p
else :
return(trimTree(p[0]),trimTree(p[1]))
where tree is:
[
13,
[ 6, [ 3, [Object], [Object] ], [ 3, 'a' ] ],
[ 7, [ 3, 'b' ], [ 4, [Object], [Object] ] ]
]
when I convert I got error:
TypeError: Cannot read property '0' of undefined
What should I do?
With a proper data structure, which means any node has only a length of two elements, you get a list of values in breaths first order (the result is here a string).
function trimTree(tree) {
var p = tree[1];
return typeof p === 'string'
? p
: trimTree(p[0]) + trimTree(p[1]);
}
var data = [
13,
[
[6,
[
[3,
[
[1, 'X'],
[2, 'Y']
]
],
[3, 'a']
]
],
[7,
[
[3, 'b'],
[4,
[
[2, 'Z'],
[2, 'Q']
]
]
]
]
]
];
console.log(trimTree(data));
I am working with javascript arrays, where i have an array of arrays like,
var arr = [
[ 73.0191641, 33.5720131 ],
[ 73.0191641, 33.5720131 ],
[ 3.0191641, 33.5720131 ],
[ 73.0191641, 33.5720131 ],
[ 73.0191641, 33.5720131 ],
[ 73.0192222, 33.5778921 ],
[ 73.0192222, 33.5778921 ]];
There, i needed to remove the duplicate arrays. I have tried this method but it didn't worked for me, may be i am missing or doing something wrong.
var distinctArr = Array.from(new Set(arr));
Although this method works only for array of objects. If someone can help, please do help. Thanks for your time.
Lodash is great lib for doing this little things.
uniqWith with compare isEqual should resolve your problem.
var arr = [
[ 73.0191641, 33.5720131 ],
[ 73.0191641, 33.5720131 ],
[ 3.0191641, 33.5720131 ],
[ 73.0191641, 33.5720131 ],
[ 73.0191641, 33.5720131 ],
[ 73.0192222, 33.5778921 ],
[ 73.0192222, 33.5778921 ]];
_.uniqWith(arr,_.isEqual)
return -> [Array(2), Array(2), Array(2)]
You can use following approach.
var arr = [ { person: { amount: [1,1] } }, { person: { amount: [1,1] } }, { person: { amount: [2,1] } }, { person: { amount: [1,2] } }, { person: { amount: [1,2] } }];
hash = [...new Set(arr.map(v => JSON.stringify(v)))].map(v => JSON.parse(v));
document.write(`<pre>${JSON.stringify(hash, null, 2)}</pre>`);
I have this input array already sorted on the key:
var sortedArray = [ [ 'de', [ 1 ] ],
[ 'elle', [ 1 ] ],
[ 'elle', [ 1 ] ],
[ 'la', [ 1 ] ],
[ 'la', [ 1 ] ],
[ 'la', [ 1 ] ],
[ 'le', [ 1 ] ],
[ 'maison', [ 1 ] ],
[ 'voiture', [ 1 ] ],
[ 'voiture', [ 1 ] ]
];
I want to obtain this reduced Array :
[ [ 'de', [ 1 ] ],
[ 'elle', [ 1, 1 ] ],
[ 'la', [ 1, 1, 1 ] ],
[ 'le', [ 1 ] ],
[ 'maison', [ 1 ] ],
[ 'voiture', [ 1, 1 ] ]
];
I proceed like that :
sortedArray.forEach((elem, index, arr) => {
if (elem[0] === arr[index + 1][0]){
arr[index][1].push(1);
arr.splice(index + 1, 1);
}
});
console.log(sortedArray);
But I can't understand why I obtain this result:
[ [ 'de', [ 1 ] ],
[ 'elle', [ 1, 1 ] ],
[ 'la', [ 1, 1 ] ],
[ 'la', [ 1 ] ],
[ 'le', [ 1 ] ],
[ 'maison', [ 1 ] ],
[ 'voiture', [ 1, 1 ] ]
]
Help would be apreciated.
The issue is that you're splicing your array while iterating over it without resetting your current index. One way to get the desired result while using splice is to do something like this:
sortedArray.forEach((elem, index, arr) => {
while (arr[index + 1] && elem[0] === arr[index + 1][0]){
arr[index][1].push(1);
arr.splice(index + 1, 1);
}
});
Basically we're changing the if statement to a while loop and adding an extra check.
Use Array.prototype.reduce to create a new array. Because the original array is sorted, you only need to push 1 to the last item in the array, as long as it's the same as the current item, and add a new item whenever that's not true:
var sortedArray = [
['de', [1]],
['elle', [1]],
['elle', [1]],
['la', [1]],
['la', [1]],
['la', [1]],
['le', [1]],
['maison', [1]],
['voiture', [1]],
['voiture', [1]]
];
var result = sortedArray.reduce(function(result, item) {
if (!result.length || item[0] !== result[result.length - 1][0]) { // check if 1st results array is empty or if current item 'key' doesn't match the last item it result
result.push([item[0], []]); // push a new 'key' item with an empty array of 1s
}
result[result.length - 1][1].push(1); // push 1 to last item in result
return result;
}, []);
console.log(result);
I am trying to write a function to flatten an array. I have part of the function working and I need help in the other half.
flatten: function(anyArray, singleLevel) {
if (singleLevel == true) {
flatArray = Array.prototype.concat.apply([], anyArray);
return flatArray;
}
flatArray = Array.prototype.concat.apply([], anyArray);
if (flatArray.length != anyArray.length) {
flatArray = someObject.array.flatten(flatArray);
}
return flatArray;
}
if I type
.flatten([[[1],[1,2,3,[4,5],4],[2,3]]], true);
I want it to flatten only one level:
[[1],[1,2,3,[4,5],4],[2,3]]
Modern JavaScript allows us to handle this very easily using a variety of techniques
Using Array.prototype.flat -
const arr =
[ [ 1 ], [ 2, 3, [ 4, 5, [ 6 ] ] ], [ 7, [ 8, 9 ] ] ]
const flatArr =
arr.flat(1) // 1 is default depth
console.log(JSON.stringify(arr))
console.log(JSON.stringify(flatArr))
// [[1],[2,3,[4,5,[6]]],[7,[8,9]]]
// [1,2,3,[4,5,[6]],7,[8,9]]
Using Array.prototype.flatMap -
const arr =
[ [ 1 ], [ 2, 3, [ 4, 5, [ 6 ] ] ], [ 7, [ 8, 9 ] ] ]
const flatArr =
arr.flatMap(x => x)
console.log(JSON.stringify(arr))
console.log(JSON.stringify(flatArr))
// [[1],[2,3,[4,5,[6]]],[7,[8,9]]]
// [1,2,3,[4,5,[6]],7,[8,9]]
Using a spread argument to Array.prototype.concat
const arr =
[ [ 1 ], [ 2, 3, [ 4, 5, [ 6 ] ] ], [ 7, [ 8, 9 ] ] ]
const flatArr =
[].concat(...arr)
console.log(JSON.stringify(arr))
console.log(JSON.stringify(flatArr))
// [[1],[2,3,[4,5,[6]]],[7,[8,9]]]
// [1,2,3,[4,5,[6]],7,[8,9]]
Older version of JavaScript (ECMAScript 5 and below) can use techniques like Function.prototype.apply -
var arr =
[ [ 1 ], [ 2, 3, [ 4, 5, [ 6 ] ] ], [ 7, [ 8, 9 ] ] ]
var flatArr =
Array.prototype.concat.apply([], arr)
console.log(JSON.stringify(arr))
console.log(JSON.stringify(flatArr))
// [[1],[2,3,[4,5,[6]]],[7,[8,9]]]
// [1,2,3,[4,5,[6]],7,[8,9]]
Using Array.prototype.reduce -
var arr =
[ [ 1 ], [ 2, 3, [ 4, 5, [ 6 ] ] ], [ 7, [ 8, 9 ] ] ]
var flatArr =
arr.reduce((r, a) => r.concat(a), [])
console.log(JSON.stringify(arr))
console.log(JSON.stringify(flatArr))
// [[1],[2,3,[4,5,[6]]],[7,[8,9]]]
// [1,2,3,[4,5,[6]],7,[8,9]]
Using a primitive for loop -
var arr =
[ [ 1 ], [ 2, 3, [ 4, 5, [ 6 ] ] ], [ 7, [ 8, 9 ] ] ]
var flatArr =
[]
for (var i = 0; i < arr.length; i = i + 1)
flatArr = flatArr.concat(arr[i])
console.log(JSON.stringify(arr))
console.log(JSON.stringify(flatArr))
// [[1],[2,3,[4,5,[6]]],[7,[8,9]]]
// [1,2,3,[4,5,[6]],7,[8,9]]
The concat array method expects one or more arrays as arguments, whose elements will be appended:
[1].concat([2, 3], [4]) // [1, 2, 3, 4]
So if you are using apply, that will flatten another level:
[].concat.apply([1], [[2], [3]]) // === [1].concat([2], [3])
So you can either use push instead of concat, or call (or just direct invocation) instead of apply to get only a single flattening level.
if you use ES6/ES2015 you can use spread operator. Something like this
console.log(...[[[1],[1,2,3,[4,5],4],[2,3]]])