I have a problem, when I used input[index] in the statement the reverse word didn't match the value of inputString. But this works in C#. When I try it in JavaScript is not working. I want to learn what are the other alternative way of .char() method. Can anybody solve my problem?
strReverse = "";
input = document.getElementById("inputValue").value;
i = input.length;
for(var j = i; j >= 0; j--) {
strReverse = strReverse + input.charAt(j); // i used input[index]
}
If you wish to use input[index] instead of input.charAt() then you need to address the issue that you are setting i = input.length;
So when you enter your loop for the first iteration, j will be equal to i. Meaning that you are trying to access the character at the index equal to the length of the string (when you do input[j]). However, as arrays and string indexing starts at zero in javascript (and in most languages), there is no index at i (the length of the string), but, there is an index at i-1, which will give the last character in the string. Thus, if you want to reverse your array using input[j] you need to start j in your for loop as j = i - 1.
Take a look at the snippet for a working example:
strReverse = "";
input = "level";
i = input.length;
for(var j = i-1; j >= 0; j--) {
strReverse = strReverse + input[j]; // i used input[index]
}
if(strReverse === input) {
alert(input +" is a palindrome!")
} else {
alert(input +" is not a palindrome!");
}
Related
Just started my uni course, struggling a little with javascript. I have been asked to display a square using any character, however, the solution must combine for loops and if statements.
This is what I have so far and I feel pretty close but I just can't get the second line to display. I know this can be done via two for loops, (one for iteration of the variable and another for spaces). But this is not how I have been asked to solve this problem.
Here is my code:
var size = 3;
let i;
for(i = 0; i < size; i++) {
print ("*");
if (size === i){
println ("");
}
}
For context, this is all taking place int he professors homemade learning environment.
You could use nested for loops and take a line break after each filled line.
function print(s) { document.getElementById('out').innerHTML += s; }
function println(s) { document.getElementById('out').innerHTML += s + '\n'; }
var size = 5,
i, j;
for (i = 0; i < size; i++) {
for (j = 0; j < size; j++) {
print("*");
}
println("");
}
<pre id="out"></pre>
Single loop with a check if i is unequal to zero and if the remainder is zero, then add a line break.
Using:
=== identity/strict equality operator checks the type and the value, for example if both are numbers and if the value is the same,
!== non-identity/strict inequality operator it is like above, but it checks the oposite of it,
% remainder operator, which returns a rest of a number which division returns an integer number.
&& logical AND operator, which check both sides and returns the last value if both a truthy (like any array, object, number not zero, a not empty string, true), or the first, if it is falsy (like undefined, null, 0, '' (empty string), false, the oposite of truthy).
function print(s) { document.getElementById('out').innerHTML += s; }
function println(s) { document.getElementById('out').innerHTML += s + '\n'; }
var size = 5,
i;
for (i = 0; i < size * size; i++) {
if (i !== 0 && i % size === 0) {
println("");
}
print("*");
}
<pre id="out"></pre>
Well the for loop is only iterating 3 times, printing the first line. If you want a square you'll have to print 9 stars total, right? So i'm assuming, is this is the approach you'd go for, you would need to iterate not until size, but until size * size.
I'm using console.log to 'print' the square:
var dimension = 10;
var edge = '*';
var inside = ' ';
var printLine;
for (var i = 1; i <= dimension; i++) {
if (i === 1 || i === dimension) {
printline = Array(dimension + 1).join(edge);
} else {
printline = edge + Array(dimension - 1).join(inside) + edge;
}
console.log(printline);
}
Note that in the following example, an array of length 11 gets you only 10 "a"s, since Array.join puts the argument between the array elements:
Array(11).join('a'); // create string with 10 as "aaaaaaaaaa"
You wanna make a square of * where the size is the number of * on its sides?
Let's split a task into 3 parts:
where you print top side like *****
where you print middle (left and right sides) like * *
where you print bottom (same as top)
Now let's code that, I kept the code as simple as possible, this can be done in fewer lines but I think this will be easier to understand for beginners:
var size = 5;
var i = 0;
// top
for (i = 0; i < size; i++)
console.log("*");
//middle
for (var j = 0; j < size - 2; j++){
console.log("\n"); // go to next row
// middle (2 on sides with size-2 in between)
console.log("*");
for (i = 0; i < size-2; i++)
console.log(" ");
console.log("*\n"); // goes to new row as well
}
// same as top
for (i = 0; i < size; i++)
console.log("*");
Full square is even simpler:
var size = 5;
var i = 0;
for (var i = 0; i < size; i++){ // iterates rows
for (var j = 0; j < size; j++) // iterates * in row
console.log("*");
console.log("\n") // moves to new row
}
In order to print a row, you print same sign X times. Well, to print X rows we can use just that 1 more time (only this time we are iterating over a different variable (j is * in a row, i is a number of rows).
After a row is made we go to go to next row with \n.
As for
it must contain if statement
Put this at the end:
if (youCanHandleTheTruth) console.log("It's a terrible practice to tell students their solution MUST CONTAIN CODEWORDS. If you need them to showcase something, write appropriate task that will require them to do so.");
Here is the code in question:
var L1 = [];
var Q1 = [];
function populateListOne() {
var limit = prompt("please enter a number you would like to fill L1 to.");
for (i = 2; i <= limit; i++) {
L1[i] = i;
}
for (n = 2; n <= L1.length; n++) {
var count = 2;
if (n == count) {
var index = L1.indexOf(n);
L1.splice(index, 1);
Q1[n] = n;
count = count + 1;
}
for (j = 0; j <= L1.length; j++) {
if (L1[j] % 2 == 0) {
var secondIndex = L1.indexOf(j);
L1.splice(secondIndex, 1);
}
}
}
document.getElementById("demo").innerHTML = "iteration " + "1" + ": " + L1 + " Q1 = " + Q1;
}
I’m currently working on a homework assignment where I have to setup a queue. All is explained in my JSFiddle.
Problem description
Essentially, the part I’m stuck on is iterating through each instance of the array and then taking the value out if the modulus is identical to 0. However, as you can see when I run the program, it doesn’t work out that way. I know the problem is in the second for loop I just don’t see what I’m doing wrong.
The way I read it is, if j is less than the length of the array, increment. Then, if the value of the index of L1[j] modulus 2 is identical to 0, set the value of secondIndex to whatever the index of j is. Then splice it out. So, theoretically, only numbers divisible by two should be removed.
Input
A single number limit, which will be used to fill array L1.
L1 will be initialized with values 2, 3, ... limit.
Process
Get the starting element of array L1 and place it in array Q1.
Using that element, remove all values in array L1 that are divisible by that number.
Repeat until array L1 is empty.
You're going to have issues with looping over an array if you're changing the array within the loop. To help with this, I tend to iterate from back to front (also note: iterate from array.length - 1 as the length element does not exist, arrays are key'd from 0):
for(j = L1.length - 1; j >=0 ; j--)
For your first loop, you miss the elements L1[0] and L1[1], so I would change the first loop to:
L1 = [];
for(i = 2; i <= limit; i++)
{
L1.push(i);
}
In this section:
for(j = 0; j <= L1.length; j++){
if(L1[j] % 2 == 0)
{
var secondIndex = L1.indexOf(j);
L1.splice(secondIndex, 1);
}
}
you should splice with j instead of secondIndex.
Change L1.splice(secondIndex, 1); to L1.splice(j, 1);
Array indices and putting entries
You initial code used an array that was initialized to start at index 2. To avoid confusion, of what index to start at, start with index 0 and iterate until array.length instead of a predefined value limit to ensure that you go through each element.
The following still works but will be more of a headache because you need remember where to start and when you will end.
for (i = 2; i <= limit; i++) {
L1[i] = i; // 'i' will begin at two!
}
Here's a better way:
for (i = 2; i <= limit; i++) {
// 'i' starts at 2 and since L1 is an empty array,
// pushing elements into it will start index at 0!
L1.push(i);
}
Use pop and slice when getting values
When you need to take a peek at what value is at the start of your array, you can do so by using L1[0] if you followed my advice above regarding array keys.
However, when you are sure about needing to remove the starting element of the array, use Array.slice(idx, amt). idx specifies which index to start at, and amt specifies how many elements to remove beginning at that index (inclusive).
// Go to 1st element in L1. Remove (1 element at index 0) from L1.
var current = L1.splice(0, 1);
Use the appropriate loops
To make your life easier, use the appropriate loops when necessary. For loops are used when you know exactly how many times you will iterate. Use while loops when you are expecting an event.
In your case, 'repeat until L1 is empty' directly translates to:
do {
// divisibility checking
} while (L1.length > 0);
JSFiddle
Here's a complete JS fiddle with in-line comments that does exactly what you said.
I'm very new to Javascript and trying to create a script that will run an action if it finds a particular set of characters in the open document's name. Right now I've got this which doesn't do anything, but I think it might be on the right track?
var name = activeDocument.name
var mRP = "mrp"
var hits = []
for(var i = 0 ; i < name.length ; i++){
if(name[i] === mRP[0]){
for(var j = i ; j < i + mRP.length ; j++){
if(name.substring(j, j + mRP.length)===mRP)
hits.push(name.substring(j, j + mRP.length));
}
}
if(hits[0] === "mrp"){
app.doAction ('Make Crease', 'MR P')
}
}
I'm looking for the action to run if it finds mrp in the document's title.. usually structured like BC342D_mrp_cu
You can search through the activeDocument.name string using regular expression and just do your action every time it finds "mrp" substring.
var name = activeDocument.name
var regex = /mrp/gi;
while ( regex.exec(name) )
app.doAction ('Make Crease', 'MRP');
Here is fiddle: http://jsfiddle.net/g3hnnf3o/
I am trying to make a simple website where the user types input into a search box, and every time a key is press, their input is compared against the first row of a 2 dimensional array which checks for character matches. If the character they input doesn't match anything, I want it to remove that specific bucket of the array. I have attempted to write basic code for this I thought would work, and have it up at the demo site linked. (Sorry I am just using a free host and havn't optimized the equation table at all so bear with it)
http://fakefakebuzz.0fees.net/
As you can see, the function is not eliminating the appropriate table rows. For example, typing "A" should not eliminate the "Average Current Equation" row because the first letter of that is A, which means matches should not = 0.
I have been looking through this code all morning, and cannot find where I went wrong. I also want to stick to vanilla js.
Any help?
Thanks so much.
I just debugged your code, and the function you use is narrowTable. first remove onkeypress from body node
<body onload="printTable()" onkeypress="narrowTable()">
and add onkeyup instead to you input, like this:
<input type="search" name="equationSearch" id="equationSearch"
placeholder="Equation Search" autofocus="" onkeyup="narrowTable()">
because when you use onkeypress the key value hasn't been added to the input box and your input value has no value in your function, which is:
function narrowTable() {
var newTableContent = "";
var matches = 0;
var input = document.getElementById("equationSearch").value;
//input has no value
for (var i = 0; i < tableData.length; i++) {
for (var j = 0; j < tableData[i][0].length; j++) {
if (input == tableData[i][0].charAt(j)) {
matches++;
}
}
if (matches == 0) {
tableData.splice(i, 1);
}
matches = 0;
}
for (var i = 0; i < tableData.length; i++) {
newTableContent += "<tr><td>" + tableData[i][0] + "</td><td>" + tableData[i][1] + "</td></tr>";
}
document.getElementById("table").innerHTML = newTableContent;
}
the other problem your code has is after printing your table, your tableData variable has changed because you have removed some of indexes. you should reset the tableData to its original value or you can do:
function narrowTable() {
//create a copy of your original array and use currenttableData instead
var currenttableData = tableData.slice();
var newTableContent = "";
var matches = 0;
//your code
}
the other problem here is the way you search for your input value:
for (var j = 0; j < tableData[i][0].length; j++) {
if (input == tableData[i][0].charAt(j)) {
matches++;
}
}
if (matches == 0) {
tableData.splice(i, 1);
}
you can easily do this, instead:
if(tableData[i][0].search("input") == -1){
tableData.splice(i, 1);
}
First, to check if a string is a substring of another string, you can use indexOf. It will return -1 if the string is not found in the other string.
Second, you shouldn't alter the array while you are still looping through it, unless you make sure to alter the counter variable (i in this case) appropriately.
var dataToRemove = [],
i;
for (i=0; i<tableData.length; i++) {
if(tableData[i][0].indexOf(input) == -1) {
// add the index to the to-be-removed array
dataToRemove.push(i);
}
// remove them in reverse order, so the indices don't get shifted as the array gets smaller
for(i = dataToRemove.length - 1; i >= 0; i--) {
tableData.splice(i, 1);
}
dataToRemove = [];
for (i=0; i<tableData.length; i++) {
newTableContent += "<tr><td>" + tableData[i][0] + "</td><td>" + tableData[i][1] + "</td></tr>";
}
I haven't tested this code, but it should at least give you a better idea of how to make this work.
So, i'm working on a 'for' loop that will identify my name, Andrew, and push it into an array, but there's something wrong with it
/*jshint multistr:true */
var text = ("Andrew is really awesome and Andrew should be working on the project, but there is honestly nothing for Andrew to do.");
var myName = ("Andrew");
var hits = [];
for (var i = 0; i < text.length; i ++) {
if (text[i] === "A") {
for (var j = i; i + nyName.length; i ++) {
hits.push(text[j]);
}
}
}
Also, the second loop is supposed to stop when it reaches the end of myName.
You're using JSHINT, so just read the error messages and it'll tell you exactly what's wrong.
Errors:
Line 7: for (var j = i; i + nyName.length; i ++) {
'nyName' is not defined.
Line 3: var myName = ("Andrew");
'myName' is defined but never used.
JSHINT isn't much good if you don't pay attention to what it's telling you.
Also, your inner loop looks odd.
for (var j = i; i + nyName.length; i ++) {
Seems like it'll cause an infinite loop. You're perhaps wanting j with a different condition.
You misspelled myName in your for loop syntax and typed nyName instead, so chances are the script dies as soon as it hits that line.
A typo in the for loop that wants to refer to myName would appear to be a big problem:
for (var j = i; i + nyName.length; i ++)
^
The misspelled myName isn't the only part that fails. You for loop will never end the loop because i + myName.length will always evaluate to true. You also need to increase the value of j or it will always get the character at index i.
Here's the corrected loop.
for (var i = 0; i < text.length; i ++) {
if (text[i] === "A") {
for (var j = 0; j < myName.length; i++, j++) {
hits.push(text[i]);
}
}
}