Javascript: Create a 10x10 array of 1s

Question

Obviously this challenge would be trivial with separate functions and libraries, so they aren't allowed.

Your code must conform to an ECMAscript specification (any spec will do), so no browser-specific answers.

The array must be accessible after it is instantiated.

I have an answer that I'll withhold for now.

Note: this challenge is specific to javascript because it is notoriously inconvenient to make multi-dimensional arrays in javascript.

Answer 1

Javascript, 34 bytes

for(r=[b=[i=10]];i--;r[i]=b)b[i]=1

Since it's apparently OK to make the rows equal by reference, I guess it's apparently OK to rely on that fact. This helps us shave off one for-loop by building the table at the same time as its rows. So, here's my new contestant.

Since r[0] and b[0] are overwritten during the loop, they can contain garbage. This gives us another free execution slot to shave off some commas. Sadly, r=b=[] won't do, since then they are equal by-ref.

Also, it scales well (99x99 is still 34 bytes), doesn't require ES5 (the new functions have terribly long names, anyways), and as a bonus, it's unreadable :-)

Answer 2

ECMAScript 6 - 33 Characters

x=(y=[..."1111111111"]).map(x=>y)

Outputs a 10x10 array of "1"s.

This abuses the fact that the string "1111111111" has all the requisite properties to be treated as if it is an array so you can use the spread operator ... to transform it into an array of characters and then map it to a copy of the array with each element referencing the "original".

Or with only one variable name (for 35 characters):

x=(x=x=>[..."1111111111"])().map(x)

Or for extra confusion (but at 45 characters)

x=[];x[9]=x;x=[...x].map(y=>[...x].map(x=>1))

or (43 characters)

y=y=>[...x].map(x=>y);x=[];x[9]=x;x=y(y(1))

Answer 3

44 bytes

for(a=[i=10];i;)a[--i]=[1,1,1,1,1,1,1,1,1,1]

Previous version:

for(a=i=[];i^10;)a[i++]=[1,1,1,1,1,1,1,1,1,1]

Answer 4

45 characters

x=[a=[1,1,1,1,1,1,1,1,1,1],a,a,a,a,a,a,a,a,a]

Each element points to the same array, but the spec doesn't mention anything against that!

Answer 5

Javascript ES6, 30

(x=i=>Array(10).fill(i))(x(1))

ES6 in action :)

Answer 6

Javascript, 51

a=[];for(i=10;i;i--,a.push([1,1,1,1,1,1,1,1,1,1]));

Or if all indices are allowed to point to the same array:

Javascript, 41

a=[1,1,1,1,1,1,1,1,1,1];a=a.map(a.sort,a)

Answer 7

JavaScript, 45 44 Bytes

Best I have so far. (Still trying).

x=[];while(x.push([1,1,1,1,1,1,1,1,1,1])-10);

Shorter (thanks mellamokb!)

for(x=[];x.push([1,1,1,1,1,1,1,1,1,1])-10;);

Answer 8

Javascript, 47

Since my original solution has been beaten, I will now post it.

for(a=[],i=10;i--;a[i]='1111111111'.split(''));

Unfortunately, 0x3FF.toString(2) isn't quite as efficient as just listing the string out, which isn't quite as efficient as just statically declaring the array.

You can shave off one character this way (46):

for(a=[],i=10;i--;a[i]=[1,1,1,1,1,1,1,1,1,1]);

You can save 2 more characters like so: (44)

for(a=[i=10];i--;)a[i]=[1,1,1,1,1,1,1,1,1,1]

Another 44 byte solution using JS 1.8 function expression closures (FF only atm):

x=(x=[1,1,1,1,1,1,1,1,1,1]).map(function()x)

Answer 9

JavaScript, 57 bytes

r=eval("["+(A=Array(11)).join("["+A.join("1,")+"],")+"]")

Before golfing:

a=Array(11).join("1,");
b=Array(11).join("["+a+"],")
c=eval("["+b+"]")

Note: This needs ES5, so don't expect much from IE.

Answer 10

54

This has already been beaten, but here's my solution:

function x(){return[1,1,1,1,1,1,1,1,1,1]}x=x().map(x)

Answer 11

39 bytes

Using array comprehension in ECMAScript 7:

x=[x for(y in x=[1,1,1,1,1,1,1,1,1,1])]

Answer 12

56 characters

Rather long answer, but will be better for 100x100 etc.

for(a=[[i=k=0]];++i<100;m?0:a[k=i/10]=[1])a[k][m=i%10]=1

Answer 13

Javascript, 36 chars (ECMA 6)

(a=[b=[]]).fill(b.fill(a[9]=b[9]=1))

Tested in my browser (Firefox on Ubuntu) and in the Codecademy Javascript interpreter

Answer 14

ES6, 54

It's not the shortest, but I thought I'd go for a different approach to what's already here.

a=(''+{}).split('').slice(0,10).map(_=>a.map(_=>1))

Cast an object to a string "[object Object]"
Split the string into chars ["[", "o", "b", ... "]" ]
Grab a slice of just 10
Map the result of mapping 1 onto the initial slice

Answer 15

61 for fun

eval("r=["+("["+(Array(11).join("1,"))+"],").repeat(11)+"]")

Answer 16

Javascript - 64 63 59 characters

for(var a=b=[],i=100;i-->0;b[i%10]=1)if(i%10==0){a[i/10]=b;b=[]}

for(var a=b=[i=100];i-->0;b[i%10]=1)if(i%10==0){a[i/10]=b;b=[]}

One char saved by hiding the iterator in the array.

for(a=b=[1],i=100;i--;b[i%10]=1)if(i%10==0){a[i/10]=b;b=[]}

Saved some chars with Jans suggestions.

Readable version:

for(var a = b = [i = 100]; i-- > 0; b[i % 10] = 1) {
  if(i % 10 == 0) {
    a[i / 10] = b;
    b = [];
  }
}

Yes, it's not the shortest solution, but another approach without using readymade [1,1,1,1,1,1,1,1,1,1] arrays.

Answer 17

Javascript 69 characters (for now)

b=[]
a=[]
for(i=100;i-->0;){
a.push(1)
if(i%10===0){b.push(a);a=[]}
}

Answer 18

JavaScript 73

function h(){s="1111111111",r=[10],i=-1;while(++i<10){r[i]=s.split("");}}

Answer 19

Javascript ES6, 53

x="1".repeat(100).match(/.{10}/g).map(s=>s.split(""))

But the ones in the array are strings :)

Answer 20

Javscript ES6, 53

x=eval("["+("["+"1,".repeat(10)+"],").repeat(10)+"]")

Answer 21

JavaScript (ES6), 35 bytes

A=Array(10).fill(Array(10).fill(1))