Can't get function to find multiple indexes of identical string in array
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Multi tool use
I found this indexOf-Tryit on W3schools and decided to try modifying it into a function that finds index values for each instance of "Apple" and outputs them to a paragraph. I cannot get it to work and it's driving me mad.
I've tried using for and while-loops with many different variations.
function myFunction() {
var fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
for (i=0; i < fruits.length; i++) {
if (fruits[i] = fruits.indexOf("Apple")) {
document.getElementById("demo").innerHTML += fruits[i];
} else {
document.getElementById("demo").innerHTML += "x"}
}
}
I want the paragraph to display "0x2x45xx8x10" or "0245810" without the else-operation. What I get instead is "x224458881010".
javascript arrays
add a comment |
I found this indexOf-Tryit on W3schools and decided to try modifying it into a function that finds index values for each instance of "Apple" and outputs them to a paragraph. I cannot get it to work and it's driving me mad.
I've tried using for and while-loops with many different variations.
function myFunction() {
var fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
for (i=0; i < fruits.length; i++) {
if (fruits[i] = fruits.indexOf("Apple")) {
document.getElementById("demo").innerHTML += fruits[i];
} else {
document.getElementById("demo").innerHTML += "x"}
}
}
I want the paragraph to display "0x2x45xx8x10" or "0245810" without the else-operation. What I get instead is "x224458881010".
javascript arrays
Sounds like you want this: jsfiddle.net/khrismuc/wL8un027 (main issue:=
is for assignment; for comparisons you need==
or===
. And please don't use w3schools)
– Chris G
Dec 30 '18 at 20:30
Why should I not use W3schools? Please elaborate.
– user62840
Dec 31 '18 at 11:59
meta.stackoverflow.com/questions/280478/why-not-w3schools-com
– Chris G
Dec 31 '18 at 12:01
add a comment |
I found this indexOf-Tryit on W3schools and decided to try modifying it into a function that finds index values for each instance of "Apple" and outputs them to a paragraph. I cannot get it to work and it's driving me mad.
I've tried using for and while-loops with many different variations.
function myFunction() {
var fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
for (i=0; i < fruits.length; i++) {
if (fruits[i] = fruits.indexOf("Apple")) {
document.getElementById("demo").innerHTML += fruits[i];
} else {
document.getElementById("demo").innerHTML += "x"}
}
}
I want the paragraph to display "0x2x45xx8x10" or "0245810" without the else-operation. What I get instead is "x224458881010".
javascript arrays
I found this indexOf-Tryit on W3schools and decided to try modifying it into a function that finds index values for each instance of "Apple" and outputs them to a paragraph. I cannot get it to work and it's driving me mad.
I've tried using for and while-loops with many different variations.
function myFunction() {
var fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
for (i=0; i < fruits.length; i++) {
if (fruits[i] = fruits.indexOf("Apple")) {
document.getElementById("demo").innerHTML += fruits[i];
} else {
document.getElementById("demo").innerHTML += "x"}
}
}
I want the paragraph to display "0x2x45xx8x10" or "0245810" without the else-operation. What I get instead is "x224458881010".
javascript arrays
javascript arrays
edited Dec 30 '18 at 20:26
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
Carcigenicate
17.6k43158
17.6k43158
asked Dec 30 '18 at 20:25
user62840user62840
61
61
Sounds like you want this: jsfiddle.net/khrismuc/wL8un027 (main issue:=
is for assignment; for comparisons you need==
or===
. And please don't use w3schools)
– Chris G
Dec 30 '18 at 20:30
Why should I not use W3schools? Please elaborate.
– user62840
Dec 31 '18 at 11:59
meta.stackoverflow.com/questions/280478/why-not-w3schools-com
– Chris G
Dec 31 '18 at 12:01
add a comment |
Sounds like you want this: jsfiddle.net/khrismuc/wL8un027 (main issue:=
is for assignment; for comparisons you need==
or===
. And please don't use w3schools)
– Chris G
Dec 30 '18 at 20:30
Why should I not use W3schools? Please elaborate.
– user62840
Dec 31 '18 at 11:59
meta.stackoverflow.com/questions/280478/why-not-w3schools-com
– Chris G
Dec 31 '18 at 12:01
Sounds like you want this: jsfiddle.net/khrismuc/wL8un027 (main issue:
=
is for assignment; for comparisons you need ==
or ===
. And please don't use w3schools)– Chris G
Dec 30 '18 at 20:30
Sounds like you want this: jsfiddle.net/khrismuc/wL8un027 (main issue:
=
is for assignment; for comparisons you need ==
or ===
. And please don't use w3schools)– Chris G
Dec 30 '18 at 20:30
Why should I not use W3schools? Please elaborate.
– user62840
Dec 31 '18 at 11:59
Why should I not use W3schools? Please elaborate.
– user62840
Dec 31 '18 at 11:59
meta.stackoverflow.com/questions/280478/why-not-w3schools-com
– Chris G
Dec 31 '18 at 12:01
meta.stackoverflow.com/questions/280478/why-not-w3schools-com
– Chris G
Dec 31 '18 at 12:01
add a comment |
2 Answers
2
active
oldest
votes
Problem was if (fruits[i] = fruits.indexOf("Apple"))
you're changing value of fruits[i]. Moreover you can directly compare the value and use the index as you're already looping through array.
function myFunction() {
var fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
for (i=0; i < fruits.length; i++) {
if (fruits[i] === "Apple") {
document.getElementById("demo").innerHTML += i;
} else {
document.getElementById("demo").innerHTML += "x"}
}
}
myFunction()
<div id='demo'>
</div>
add a comment |
Another approach is to map
the string values to the index value if they match. If they don't match set a falsy value. Then use filter
to remove all non matching values.
Passing in the array to be searched and the value you're looking for makes the function more reusable. And not returning a string allows the function to more flexible still. It's easy enough to join an array with .join(',')
function findIndexesOf(arr, value) {
return arr.map((e, i) => e == value ? i : null).filter( e => e != null)
}
let fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
let appleIndexs = findIndexesOf(fruits, "Apple")
console.log("Apples:", appleIndexs.join(','))
console.log(appleIndexs)
let mangoIndexs = findIndexesOf(fruits, "Mango")
console.log(mangoIndexs)
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
Problem was if (fruits[i] = fruits.indexOf("Apple"))
you're changing value of fruits[i]. Moreover you can directly compare the value and use the index as you're already looping through array.
function myFunction() {
var fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
for (i=0; i < fruits.length; i++) {
if (fruits[i] === "Apple") {
document.getElementById("demo").innerHTML += i;
} else {
document.getElementById("demo").innerHTML += "x"}
}
}
myFunction()
<div id='demo'>
</div>
add a comment |
Problem was if (fruits[i] = fruits.indexOf("Apple"))
you're changing value of fruits[i]. Moreover you can directly compare the value and use the index as you're already looping through array.
function myFunction() {
var fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
for (i=0; i < fruits.length; i++) {
if (fruits[i] === "Apple") {
document.getElementById("demo").innerHTML += i;
} else {
document.getElementById("demo").innerHTML += "x"}
}
}
myFunction()
<div id='demo'>
</div>
add a comment |
Problem was if (fruits[i] = fruits.indexOf("Apple"))
you're changing value of fruits[i]. Moreover you can directly compare the value and use the index as you're already looping through array.
function myFunction() {
var fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
for (i=0; i < fruits.length; i++) {
if (fruits[i] === "Apple") {
document.getElementById("demo").innerHTML += i;
} else {
document.getElementById("demo").innerHTML += "x"}
}
}
myFunction()
<div id='demo'>
</div>
Problem was if (fruits[i] = fruits.indexOf("Apple"))
you're changing value of fruits[i]. Moreover you can directly compare the value and use the index as you're already looping through array.
function myFunction() {
var fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
for (i=0; i < fruits.length; i++) {
if (fruits[i] === "Apple") {
document.getElementById("demo").innerHTML += i;
} else {
document.getElementById("demo").innerHTML += "x"}
}
}
myFunction()
<div id='demo'>
</div>
function myFunction() {
var fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
for (i=0; i < fruits.length; i++) {
if (fruits[i] === "Apple") {
document.getElementById("demo").innerHTML += i;
} else {
document.getElementById("demo").innerHTML += "x"}
}
}
myFunction()
<div id='demo'>
</div>
function myFunction() {
var fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
for (i=0; i < fruits.length; i++) {
if (fruits[i] === "Apple") {
document.getElementById("demo").innerHTML += i;
} else {
document.getElementById("demo").innerHTML += "x"}
}
}
myFunction()
<div id='demo'>
</div>
edited Dec 30 '18 at 20:38
answered Dec 30 '18 at 20:32
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Code ManiacCode Maniac
4,6011219
4,6011219
add a comment |
add a comment |
Another approach is to map
the string values to the index value if they match. If they don't match set a falsy value. Then use filter
to remove all non matching values.
Passing in the array to be searched and the value you're looking for makes the function more reusable. And not returning a string allows the function to more flexible still. It's easy enough to join an array with .join(',')
function findIndexesOf(arr, value) {
return arr.map((e, i) => e == value ? i : null).filter( e => e != null)
}
let fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
let appleIndexs = findIndexesOf(fruits, "Apple")
console.log("Apples:", appleIndexs.join(','))
console.log(appleIndexs)
let mangoIndexs = findIndexesOf(fruits, "Mango")
console.log(mangoIndexs)
add a comment |
Another approach is to map
the string values to the index value if they match. If they don't match set a falsy value. Then use filter
to remove all non matching values.
Passing in the array to be searched and the value you're looking for makes the function more reusable. And not returning a string allows the function to more flexible still. It's easy enough to join an array with .join(',')
function findIndexesOf(arr, value) {
return arr.map((e, i) => e == value ? i : null).filter( e => e != null)
}
let fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
let appleIndexs = findIndexesOf(fruits, "Apple")
console.log("Apples:", appleIndexs.join(','))
console.log(appleIndexs)
let mangoIndexs = findIndexesOf(fruits, "Mango")
console.log(mangoIndexs)
add a comment |
Another approach is to map
the string values to the index value if they match. If they don't match set a falsy value. Then use filter
to remove all non matching values.
Passing in the array to be searched and the value you're looking for makes the function more reusable. And not returning a string allows the function to more flexible still. It's easy enough to join an array with .join(',')
function findIndexesOf(arr, value) {
return arr.map((e, i) => e == value ? i : null).filter( e => e != null)
}
let fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
let appleIndexs = findIndexesOf(fruits, "Apple")
console.log("Apples:", appleIndexs.join(','))
console.log(appleIndexs)
let mangoIndexs = findIndexesOf(fruits, "Mango")
console.log(mangoIndexs)
Another approach is to map
the string values to the index value if they match. If they don't match set a falsy value. Then use filter
to remove all non matching values.
Passing in the array to be searched and the value you're looking for makes the function more reusable. And not returning a string allows the function to more flexible still. It's easy enough to join an array with .join(',')
function findIndexesOf(arr, value) {
return arr.map((e, i) => e == value ? i : null).filter( e => e != null)
}
let fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
let appleIndexs = findIndexesOf(fruits, "Apple")
console.log("Apples:", appleIndexs.join(','))
console.log(appleIndexs)
let mangoIndexs = findIndexesOf(fruits, "Mango")
console.log(mangoIndexs)
function findIndexesOf(arr, value) {
return arr.map((e, i) => e == value ? i : null).filter( e => e != null)
}
let fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
let appleIndexs = findIndexesOf(fruits, "Apple")
console.log("Apples:", appleIndexs.join(','))
console.log(appleIndexs)
let mangoIndexs = findIndexesOf(fruits, "Mango")
console.log(mangoIndexs)
function findIndexesOf(arr, value) {
return arr.map((e, i) => e == value ? i : null).filter( e => e != null)
}
let fruits = ["Apple", "Orange", "Apple", "Mango", "Apple", "Apple", "Tahiti", "Mango", "Apple", "Mango", "Apple"];
let appleIndexs = findIndexesOf(fruits, "Apple")
console.log("Apples:", appleIndexs.join(','))
console.log(appleIndexs)
let mangoIndexs = findIndexesOf(fruits, "Mango")
console.log(mangoIndexs)
answered Dec 30 '18 at 23:09
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LexLex
2,05512341
2,05512341
add a comment |
add a comment |
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0Lk9zIDJ5tYO4Ag
Sounds like you want this: jsfiddle.net/khrismuc/wL8un027 (main issue:
=
is for assignment; for comparisons you need==
or===
. And please don't use w3schools)– Chris G
Dec 30 '18 at 20:30
Why should I not use W3schools? Please elaborate.
– user62840
Dec 31 '18 at 11:59
meta.stackoverflow.com/questions/280478/why-not-w3schools-com
– Chris G
Dec 31 '18 at 12:01