Mixing
How to iterate through an array of arrays while using an expression within the indices
2
When I run the below JavaScript code the first two lines of output are:
5
undefined
Why is the second output line undefined and not 5? Here is the code:
matrix = [
[2, 5, 7],
[4, 6, 1],
[7, 3, 9]
];
for (var i in matrix) {
for (var j in matrix[i]) {
console.log(matrix[0][0 + 1]);
console.log(matrix[i][j + 1]);
}
}javascript
edited Jan 2 at 4:58
Jack Bashford
11.7k31846
asked Jan 2 at 2:37
okcappokcapp
132212
add a comment |
2
When I run the below JavaScript code the first two lines of output are:
5
undefined
Why is the second output line undefined and not 5? Here is the code:
matrix = [
[2, 5, 7],
[4, 6, 1],
[7, 3, 9]
];
for (var i in matrix) {
for (var j in matrix[i]) {
console.log(matrix[0][0 + 1]);
console.log(matrix[i][j + 1]);
}
}javascript
edited Jan 2 at 4:58
Jack Bashford
11.7k31846
asked Jan 2 at 2:37
okcappokcapp
132212
5
Don't usefor...inwith arrays, it hould be used with objects, in your code bothiandjare strings, soj + 1will not be what you expect it to be. It also loops the array out of order
– ibrahim mahrir
Jan 2 at 2:41
Becausejis the string"0"."0" + 1is"01", not1. Related: Javascript - For Loop key undefined ONLY for 1st iteration?.
– Xufox
Jan 2 at 2:43
1
It’s also explained here, in Why is using “for…in” with array iteration a bad idea?.
– Xufox
Jan 2 at 2:52
@Xufox The link you shared solved the problem. Thanks...
– okcapp
Jan 2 at 3:09
add a comment |
2
2
2
When I run the below JavaScript code the first two lines of output are:
5
undefined
Why is the second output line undefined and not 5? Here is the code:
matrix = [
[2, 5, 7],
[4, 6, 1],
[7, 3, 9]
];
for (var i in matrix) {
for (var j in matrix[i]) {
console.log(matrix[0][0 + 1]);
console.log(matrix[i][j + 1]);
}
}javascript
edited Jan 2 at 4:58
Jack Bashford
11.7k31846
asked Jan 2 at 2:37
okcappokcapp
132212
When I run the below JavaScript code the first two lines of output are:
5
undefined
Why is the second output line undefined and not 5? Here is the code:
matrix = [
[2, 5, 7],
[4, 6, 1],
[7, 3, 9]
];
for (var i in matrix) {
for (var j in matrix[i]) {
console.log(matrix[0][0 + 1]);
console.log(matrix[i][j + 1]);
}
}matrix = [
[2, 5, 7],
[4, 6, 1],
[7, 3, 9]
];
for (var i in matrix) {
for (var j in matrix[i]) {
console.log(matrix[0][0 + 1]);
console.log(matrix[i][j + 1]);
}
}matrix = [
[2, 5, 7],
[4, 6, 1],
[7, 3, 9]
];
for (var i in matrix) {
for (var j in matrix[i]) {
console.log(matrix[0][0 + 1]);
console.log(matrix[i][j + 1]);
}
}javascript
javascript
edited Jan 2 at 4:58
Jack Bashford
11.7k31846
asked Jan 2 at 2:37
okcappokcapp
132212
edited Jan 2 at 4:58
Jack Bashford
11.7k31846
asked Jan 2 at 2:37
okcappokcapp
132212
edited Jan 2 at 4:58
Jack Bashford
11.7k31846
edited Jan 2 at 4:58
Jack Bashford
11.7k31846
edited Jan 2 at 4:58
Jack Bashford
11.7k31846
11.7k31846
asked Jan 2 at 2:37
okcappokcapp
132212
asked Jan 2 at 2:37
okcappokcapp
132212
asked Jan 2 at 2:37
okcappokcapp
132212
132212
5
Don't usefor...inwith arrays, it hould be used with objects, in your code bothiandjare strings, soj + 1will not be what you expect it to be. It also loops the array out of order
– ibrahim mahrir
Jan 2 at 2:41
Becausejis the string"0"."0" + 1is"01", not1. Related: Javascript - For Loop key undefined ONLY for 1st iteration?.
– Xufox
Jan 2 at 2:43
1
It’s also explained here, in Why is using “for…in” with array iteration a bad idea?.
– Xufox
Jan 2 at 2:52
@Xufox The link you shared solved the problem. Thanks...
– okcapp
Jan 2 at 3:09
add a comment |
5
Don't usefor...inwith arrays, it hould be used with objects, in your code bothiandjare strings, soj + 1will not be what you expect it to be. It also loops the array out of order
– ibrahim mahrir
Jan 2 at 2:41
Becausejis the string"0"."0" + 1is"01", not1. Related: Javascript - For Loop key undefined ONLY for 1st iteration?.
– Xufox
Jan 2 at 2:43
1
It’s also explained here, in Why is using “for…in” with array iteration a bad idea?.
– Xufox
Jan 2 at 2:52
@Xufox The link you shared solved the problem. Thanks...
– okcapp
Jan 2 at 3:09
5
5
Don't use
for...in with arrays, it hould be used with objects, in your code both i and j are strings, so j + 1 will not be what you expect it to be. It also loops the array out of order– ibrahim mahrir
Jan 2 at 2:41
Don't use
for...in with arrays, it hould be used with objects, in your code both i and j are strings, so j + 1 will not be what you expect it to be. It also loops the array out of order– ibrahim mahrir
Jan 2 at 2:41
Because
j is the string "0". "0" + 1 is "01", not 1. Related: Javascript - For Loop key undefined ONLY for 1st iteration?.– Xufox
Jan 2 at 2:43
Because
j is the string "0". "0" + 1 is "01", not 1. Related: Javascript - For Loop key undefined ONLY for 1st iteration?.– Xufox
Jan 2 at 2:43
1
1
It’s also explained here, in Why is using “for…in” with array iteration a bad idea?.
– Xufox
Jan 2 at 2:52
It’s also explained here, in Why is using “for…in” with array iteration a bad idea?.
– Xufox
Jan 2 at 2:52
@Xufox The link you shared solved the problem. Thanks...
– okcapp
Jan 2 at 3:09
@Xufox The link you shared solved the problem. Thanks...
– okcapp
Jan 2 at 3:09
add a comment |
2 Answers
2
active
oldest
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0
oNot sure why you are trying to +1. This is causing your issue.
Also included array.forEach of this as well.
Included fix based on Ibrahim comment
matrix = [[2, 5, 7], [4, 6, 1], [7, 3, 9]];
for(let i of matrix){
for(let j of i){
console.log(j);
}
}
matrix.forEach(m => {
m.forEach(e => console.log(e));
});answered Jan 2 at 2:41
BibbertyBibberty
1,9431315
add a comment |
0
You have to cast your j variable to integer using Number() function.
matrix = [
[2, 5, 7],
[4, 6, 1],
[7, 3, 9]
];
for (var i in matrix) {
for (var j in matrix[i]) {
console.log(matrix[0][0 + 1]);
console.log(matrix[i][Number(j) + 1]);
}
}answered Jan 2 at 5:20
RAGINROSERAGINROSE
1678
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
0
oNot sure why you are trying to +1. This is causing your issue.
Also included array.forEach of this as well.
Included fix based on Ibrahim comment
matrix = [[2, 5, 7], [4, 6, 1], [7, 3, 9]];
for(let i of matrix){
for(let j of i){
console.log(j);
}
}
matrix.forEach(m => {
m.forEach(e => console.log(e));
});answered Jan 2 at 2:41
BibbertyBibberty
1,9431315
add a comment |
0
oNot sure why you are trying to +1. This is causing your issue.
Also included array.forEach of this as well.
Included fix based on Ibrahim comment
matrix = [[2, 5, 7], [4, 6, 1], [7, 3, 9]];
for(let i of matrix){
for(let j of i){
console.log(j);
}
}
matrix.forEach(m => {
m.forEach(e => console.log(e));
});answered Jan 2 at 2:41
BibbertyBibberty
1,9431315
add a comment |
0
0
0
oNot sure why you are trying to +1. This is causing your issue.
Also included array.forEach of this as well.
Included fix based on Ibrahim comment
matrix = [[2, 5, 7], [4, 6, 1], [7, 3, 9]];
for(let i of matrix){
for(let j of i){
console.log(j);
}
}
matrix.forEach(m => {
m.forEach(e => console.log(e));
});answered Jan 2 at 2:41
BibbertyBibberty
1,9431315
oNot sure why you are trying to +1. This is causing your issue.
Also included array.forEach of this as well.
Included fix based on Ibrahim comment
matrix = [[2, 5, 7], [4, 6, 1], [7, 3, 9]];
for(let i of matrix){
for(let j of i){
console.log(j);
}
}
matrix.forEach(m => {
m.forEach(e => console.log(e));
});matrix = [[2, 5, 7], [4, 6, 1], [7, 3, 9]];
for(let i of matrix){
for(let j of i){
console.log(j);
}
}
matrix.forEach(m => {
m.forEach(e => console.log(e));
});matrix = [[2, 5, 7], [4, 6, 1], [7, 3, 9]];
for(let i of matrix){
for(let j of i){
console.log(j);
}
}
matrix.forEach(m => {
m.forEach(e => console.log(e));
});answered Jan 2 at 2:41
BibbertyBibberty
1,9431315
answered Jan 2 at 2:41
BibbertyBibberty
1,9431315
answered Jan 2 at 2:41
BibbertyBibberty
1,9431315
answered Jan 2 at 2:41
BibbertyBibberty
1,9431315
1,9431315
add a comment |
add a comment |
0
You have to cast your j variable to integer using Number() function.
matrix = [
[2, 5, 7],
[4, 6, 1],
[7, 3, 9]
];
for (var i in matrix) {
for (var j in matrix[i]) {
console.log(matrix[0][0 + 1]);
console.log(matrix[i][Number(j) + 1]);
}
}answered Jan 2 at 5:20
RAGINROSERAGINROSE
1678
add a comment |
0
You have to cast your j variable to integer using Number() function.
matrix = [
[2, 5, 7],
[4, 6, 1],
[7, 3, 9]
];
for (var i in matrix) {
for (var j in matrix[i]) {
console.log(matrix[0][0 + 1]);
console.log(matrix[i][Number(j) + 1]);
}
}answered Jan 2 at 5:20
RAGINROSERAGINROSE
1678
add a comment |
0
0
0
You have to cast your j variable to integer using Number() function.
matrix = [
[2, 5, 7],
[4, 6, 1],
[7, 3, 9]
];
for (var i in matrix) {
for (var j in matrix[i]) {
console.log(matrix[0][0 + 1]);
console.log(matrix[i][Number(j) + 1]);
}
}answered Jan 2 at 5:20
RAGINROSERAGINROSE
1678
You have to cast your j variable to integer using Number() function.
matrix = [
[2, 5, 7],
[4, 6, 1],
[7, 3, 9]
];
for (var i in matrix) {
for (var j in matrix[i]) {
console.log(matrix[0][0 + 1]);
console.log(matrix[i][Number(j) + 1]);
}
}matrix = [
[2, 5, 7],
[4, 6, 1],
[7, 3, 9]
];
for (var i in matrix) {
for (var j in matrix[i]) {
console.log(matrix[0][0 + 1]);
console.log(matrix[i][Number(j) + 1]);
}
}matrix = [
[2, 5, 7],
[4, 6, 1],
[7, 3, 9]
];
for (var i in matrix) {
for (var j in matrix[i]) {
console.log(matrix[0][0 + 1]);
console.log(matrix[i][Number(j) + 1]);
}
}answered Jan 2 at 5:20
RAGINROSERAGINROSE
1678
answered Jan 2 at 5:20
RAGINROSERAGINROSE
1678
answered Jan 2 at 5:20
RAGINROSERAGINROSE
1678
answered Jan 2 at 5:20
RAGINROSERAGINROSE
1678
1678
add a comment |
add a comment |
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5
Don't use
for...inwith arrays, it hould be used with objects, in your code bothiandjare strings, soj + 1will not be what you expect it to be. It also loops the array out of order– ibrahim mahrir
Jan 2 at 2:41
Because
jis the string"0"."0" + 1is"01", not1. Related: Javascript - For Loop key undefined ONLY for 1st iteration?.– Xufox
Jan 2 at 2:43
1
It’s also explained here, in Why is using “for…in” with array iteration a bad idea?.
– Xufox
Jan 2 at 2:52
@Xufox The link you shared solved the problem. Thanks...
– okcapp
Jan 2 at 3:09