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JavaScrpit crashes when incrementing by 2 in a for loop

before you call me out for using wrong terms or sth, I am a newbie programmer.
So, this would be the correct form of the code I'm experimenting with:
for (var i = 0; i <= 10; i += 2) {
nums.push(i);
}
console.log(nums)
However, I don't get why I need to put the = sign after the +. I tried to research this but I couldn't find anything. When I removed the =, JS (Scrimba) crashed. Can anyone explain this to me please?

The third expression in the for loop is to indicate how the i variable increases. This expression is run after every loop iteration.
The second i<=10 is the condition that has to be true for the loop to continue.
Now in your loop starts with i=0, then i=2 is run after 1st iteration. And after every iteration i=2. So i<=10 is true, which is the condition. So this is an infinite loop, leading to the crash.
i+=2 is shorthand for i = i +2, so i is increasing everytime and at some point will exceed 10.
This assumes you have defined nums at top like:
var nums = []. Otherwise you get a different error.

i += 2 mean i = i + 2. In this context, for(A；B; C)，C part will run every time in every loop. If you only use "+", the i value will never changed, and loop will be non-stop considering your judgement to stop the loop i < 10 equal to 0 < 10, which is true forever.

Let's take a look at for loop before go to your problem:
for (statement 1; statement 2; statement 3) {
// code block to be executed
}
Statement 1 is executed (one time) before the execution of the code block.
Statement 2 defines the condition for executing the code block.
Statement 3 is executed (every time) after the code block has been executed.
If you want to end the loop, statement 2 should return a false value.
In your case:
statement 1 is i=1 -> Assign 1 to i variable.
statement 2 is i<=10 -> Execute the code inside brackets if and only if i is less than or equal to 10
statement 3 is i+=2 -> in crease i by 2 after every run.
the point is if you change statement 3 to i+2, it is not an assignment statement anymore, but an operator. So the value of i won't be changed after statement 3 execution.
=> The value of i will always be 1
=> the statement 2 always returns true
=> infinite loop
So your code crashes because of an infinite loop

i += 2 means your are incrementing the value of i by 2.
So, in your case, the loop will start from 0, and it will push in your array. It will keep increasing your i value by 2 and pushing them in the array till it (i) becomes more than 10

For (;;) loop explanation

In JS I stumbled across a kind of for loop which is for(;;) that functions like a while(true) loop. What do the semicolons function in the brackets of this for loop?

for (statement 1; statement 2; statement 3) {
code block to be executed
}
Statement 1 is optional and is executed before the loop (the code block) starts.
var i = 0;
var length = 10
for (; i < length; i++) {
//The for loop run until i is less than length and you incerement i by 1 each time. javascript doesnt care what you do inside, it just check whether you have variable with name i and length
}
Statement 2 is again optional defines the condition for running the loop (the code block).
var i = 0;
var len = 100;
for (i = 5; ; i++) {
//Here you are just initializing i with 5 and increment it by 1 there is no break condition so this will lead to an infinite loop hence we should always have a break here somehwere.
}
Statement 3 is optional and is executed each time after the loop (the code block) has been executed.
var i = 0;
var length = 100;
for (; i < length; ) {
//Here you are just checking for i < length which is true. If you don't increment i or have an break it will turn into infinite loop
}
In nut shell when you have no conditions or initialization's it turns into an infinite loop.

Usually, a for loop header contains 3 parts:
for (var i = 0 ; i < 10 ; i++)
// ^^^^^^^^^ ^^^^^^ ^^^
You first initialise a variable, check the condition and if it is true, do whatever the loop body says, then increment i.
What you might not know is that any part of the for loop header can be omitted. If the first part is omitted then no variable is initialised. If the second part is omitted then there is no condition check. It will always assume the condition is true.
So for(;;) is basically an infinite loop because it omitted the condition part of the for loop header. Every time, the condition is true, so it continues on forever.

for ( init; condition; increment )
{
statement(s);
}
Here is the flow of control in a for loop:
The init step is executed first, and only once. This step allows you to declare and initialize any loop control variables. You are not required to put a statement here, as long as a semicolon appears.
Next, the condition is evaluated. If it is true, the body of the loop is executed. If it is false, the body of the loop does not execute and flow of control jumps to the next statement just after the for loop.
After the body of the for loop executes, the flow of control jumps back up to the increment statement. This statement allows you to update any loop control variables. This statement can be left blank, as long as a semicolon appears after the condition.
The condition is now evaluated again. If it is true, the loop executes and the process repeats itself (body of loop, then increment step, and then again testing for a condition). After the condition becomes false, the for loop terminates.

The for loop consists of three parts:
for (INITIALIZATION; CONDITION; AFTERTHOUGHT)
{
}
If you omit these parts the whole will be evaluated as:
for(; true ;)
{ }
The initialization and after thought are just ignored.

First semi semicolon ends initialization statement.
Second semi semicolon ends condition check statement.
In your case both statement are empty (no initializing and checking nothing every loop).

Well I'm just going to take a guess.
Typically a for loop might be like this:
for (i = 0; i < 10; i++)
so basically
for (;;)
is well forever, because loop condition is always met.

What I can still add is:
reference to the source,
This conditional test is optional. If omitted, the condition always evaluates to true.
we can leave any of these three blocks in the loop for,
information that this behavior of the loop for is similar like in in C language and others with syntax inspired by C, such as C++, Java etc.,
a practical example of using such a loop:
let i = 1;
for (;;) {
if (i === 4) {
break;
}
console.log(i++);
}
I will also add that the statment block after the for loop is also optional (we only need to put the ; at the end). To show this, here's the next example: equivalent to the above code, but without the block statmant in the for loop:
for(var i = 1; i < 4; console.log(i++));

Infinite for loops are apparently tricky.

Here I am once again. This is apparently the only way I know how to learn. What I am doing is making a for loop. Yes. Something so simple. Yet, I "have" a problem with them. More or less a problem with infinite loops. What I need to do is make a loop that counts down from 10...0. It seems easy for some of you. Yes I am very aware. I am nothing more than a student learning.
This is the code that I have:
for (var i = 11; i >= 1; i++) {
console.log(i);
}
I am stuck at this point. All that it does is crash my browser every time. Help is greatly appreciated. I would like a thorough explanation of what I am doing wrong, what I should do, and why I might have made this harder than it needed to be. Thank you!

For a loop to run from 10 to 0 iterator i should be decrementing in each iteration. But you are incrementing it instead so for loop never terminates.
for (var i = 10; i>=0; i--) {
console.log(i);
}

Everyone learns differently! In this case, you're asking the code to increment (aka add) with the ++ syntax. So, if i = 1, after i++ i = 2. Similarly i-- decrements (aka subtracts) from i.
Now, the first two parts of the loop check the value of i and continue the operation. In your case, you're asking the program set i equal to 10. If i is greater than 1, add 1 to it. That's where you're getting the infinite loop because i will always be greater than 1. What you want is. for (var i = 10; i >= 0; i--) {//code here};
You could also check out while and do/while loops.

Variable i starts at 11, and is then incremented by one each loop. Since the condition is that i >= 1, it never ends. You need to change it so that i decrements by one each loop, like this:
for (var i= 11; i>=1; i--){

First you need to learn difference between increments and decrements.
increments mean to add specific value to your variable
while on other hand decrements means to reduce the value of your variable by some specific number.
Now in your case i++ means you are adding 1 to your variable i with every iteration of loop, while to end your loop you have set the condition to i>=1
this results in an infinite loop which crashes your browser, as i would never be equal to 1 or i>=1 will never be true as with each iteration the value of i increased by 1 number, so it would continue execution, until your browser crashes.
What you are looking for is:
for (var i = 10; i >= 0; i--) {
console.log(i);
}
now i will start from 10
and will gradually reduce to 0 and your loop will end.
Hope it explained.

while VS do while surprising results [duplicate]

This is a highly subjective question, so I'll be more specific. Is there any time that a do-while loop would be a better style of coding than a normal while-loop?
e.g.
int count = 0;
do {
System.out.println("Welcome to Java");
count++;
} while (count < 10);`
It doesn't seem to make sense to me to check the while condition after evaluating the do-statement (aka forcing the do statement to run at least once).
For something simple like my above example, I would imagine that:
int count = 0;
while(count < 10) {
System.out.println("Welcome to Java"); count++;
}
would be generally considered to have been written in a better writing style.
Can anyone provide me a working example of when a do-while loop would be considered the only/best option? Do you have a do-while loop in your code? What role does it play and why did you opt for the do-while loop?
(I've got an inkling feeling that the do-while loop may be of use in coding games. Correct me, game developers, if I am wrong!)

If you want to read data from a network socket until a character sequence is found, you first need to read the data and then check the data for the escape sequence.
do
{
// read data
} while ( /* data is not escape sequence */ );

The while statement continually executes a block of statements while a particular condition is true
while (expression) {
statement(s)
}
do-while evaluates its expression at the bottom of the loop, and therefore, the statements within the do block are always executed at least once.
do {
statement(s)
} while (expression);
Now will talk about functional difference,
while-loops consist of a conditional branch instructions such as if_icmpge or if_icmplt and a goto statement. The conditional instruction branches the execution to the instruction immediately after the loop and therefore terminates the loop if the condition is not met. The final instruction in the loop is a goto that branches the byte code back to the beginning of the loop ensuring the byte code keeps looping until the conditional branch is met.
A Do-while-loops are also very similar to for-loops and while-loops except that they do not require the goto instruction as the conditional branch is the last instruction and is be used to loop back to the beginning
A do-while loop always runs the loop body at least once - it skips the initial condition check. Since it skips first check, one branch will be less and one less condition to be evaluated.
By using do-while you may gain performance if the expression/condition is complex, since it is ensured to loop atleast once. In that casedo-while could call for performance gain
Very Impressive findings here,
http://blog.jamesdbloom.com/JavaCodeToByteCode_PartOne.html#while_loop

The do-while loop is basically an inverted version of the while-loop.
It executes the loop statements unconditionally the first time.
It then evaluates the conditional expression specified before executing the statements again.
int sum = 0;
int i = 0;
do
{
sum += ids[i];
i++;
} while (i < 4);
Reference material

Simply, when you want to check condition before and then perform operation while is better option, and if you want to perform operation at least once and then check the condition do-while is better.
As per your question a working example,
1. when I needed to find the field which could be declared in the same class or the super class or the super class of that super class and so on i.e. finding the field located in deep class hierarchy. (A extends B B extends C and so on)
public Field SearchFieldInHierarchy(Object classObj, String fieldName )
{
Field type = null;
Class clz = classObj.getClass();
do
{
try
{
type = clz.getDeclaredField(fieldName);
break;
} catch (NoSuchFieldException e)
{
clz = clz.getSuperclass();
}
} while(clz != null || clz != Object.class);
return type;
}
2. When reading input stream from Http response
do
{
bytesRead = inputStream.read(buffer, totalBytesRead, buffer.length - totalBytesRead);
totalBytesRead += bytesRead;
} while (totalBytesRead < buffer.length && bytesRead != 0);

You kind of answer the question yourself-when it needs to run at least once, and it makes sense to read it that way.

do - while loop allows you to ensure that the piece of code is executed at least once before it goes into the iteration.

In a while loop, the condition is tested before it executes code in the loop. In a do while loop, the code is executed before the condition is tested, resulting in the code always being executed at least once. Example:
$value = 5;
while($value > 10){
echo "Value is greater than 10";
}
The above would never output anything. If we do the same again like this:
$value = 5;
do{
echo "Value is greater than 10";
}while($value > 10)
It would output Value is greater than 10 because the condition is tested after the loop is executed. After this it would not output anything further.

The difference between do-while and while is that do-while evaluates its expression at the bottom of the loop instead of the top. Therefore, the statements within the do block are always executed at least once.
For example do check this link: http://docs.oracle.com/javase/tutorial/java/nutsandbolts/while.html

If the looping condition can only be known after a first step of the loop (when you do not want a condition before you enter the loop).
Typically:
do {
expr = ...;
while (expr);

Use the while Statement when you have to check a condition repeatedly and only when the condition is satisfied execute the loop
while(condition) //eg. a>5
{
Body of Loop
}
If you see the flow of control here you can see that the condition is checked before the execution of the loop, if the condition is not met the loop will not execute at all
In the Do-While statement the program will execute the body of the loop once and then it will check if the statement is true or not
do
{
Body of Loop
}
while(condition); //eg. a>5
If you notice the flow of control here you will see that the body is executed once, then the condition is checked. If the condition is False the Program will break out of the loop, if True it will continue executing till the condition is not satisfied
It is to be noted that while and do-while give the same output only the flow of control is different

/*
while loop
5 bucks
1 chocolate = 1 bucks
while my money is greater than 1 bucks
select chocolate
pay 1 bucks to the shopkeeper
money = money - 1
end
come to home and cant go to while shop because my money = 0 bucks
*/
#include<stdio.h>
int main(){
int money = 5;
while( money >= 1){
printf("inside the shopk and selecting chocolate\n");
printf("after selecting chocolate paying 1 bucks\n");
money = money - 1 ;
printf("my remaining moeny = %d\n", money);
printf("\n\n");
}
printf("dont have money cant go inside the shop, money = %d", money);
return 0;
}
infinite money
while( codition ){ // condition will always true ....infinite loop
statement(s)
}
please visit this video for better understanding
https://www.youtube.com/watch?v=eqDv2wxDMJ8&t=25s

It is very simple to distinguish between the two. Let's take While loop first.
The syntax of while loop is as follows:
// expression value is available, and its value "matter".
// if true, while block will never be executed.
while(expression) {
// When inside while block, statements are executed, and
// expression is again evaluated to check the condition.
// If the condition is true, the while block is again iterated
// else it exists the while block.
}
Now, let's take the do-while loop.
The syntax of do-while is different:
// expression value is available but "doesn't matter" before this loop, & the
// control starts executing the while block.
do {
// statements are executed, and the
// statements is evaluated and to check the condition. If true
// the while block is iterated, else it exits.
} while(expression);
A sample program is given below to make this concept clear:
public class WhileAndDoWhile {
public static void main(String args[]) {
int i = 10;
System.out.println("While");
while (i >= 1) {
System.out.println(i);
i--;
}
// Here i is already 0, not >= 1.
System.out.println("do-while");
do {
System.out.println(i);
i--;
} while (i >= 1);
}
}
Compile and run this program, and the difference becomes apparent.

JavaScript: What will break, and what will break it? [closed]

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Potentially dangerous code below, line 2
Repeat: POTENTIALLY DANGEROUS CODE BELOW
var history = "";
for (start = 3; start = 1000; start += 1){
if(start % 5 == 0 || start % 3 == 0)
history += start + " "; }
Okay, this is the tenth time I've put JavaScript code in that's frozen my browser. It's putting my computer in shock. Are these panic attacks going to destroy her heart? Where can I learn about all the crap that might break my computer as I continue to learn and practice JavaScript? I'm looking for an exhaustive list, only.

Your loop: for (start = 3; start = 1000; start += 1){
The second part of a for( ; ; ) loop is the condition test. The loop will continue until the second part evaluates to false. To not create an infinite loop, change your code to:
for (var start = 3; start < 1000; start += 1){
Note: start+=1 is equal to start++. If you want a compact code, you can replace +=1 by ++.
An overview of the three-part for-loop, for(initialise; condition; increment):
initialise - Create variables (allowed to be empty)
condition - The loop will stop once this expression evaluates to false
increment - This expression is executed at the end of the loop
Always check against infinite loops: Make sure that the condition is able to evaluate to false.
Commonly made mistakes:
A negative incremental expression in conjunction with a is-lower-than comparison:
i-- decreases the counter, so i<100 will always be true (unless the variable i is initialized at 100)
A positive incremental expression in conjunction with a is-higher-than comparison.
A non-incrementing expression: for(var i=0,j=0; i<100; j++) (i doesn't increase)
A condition which is always true (such as in your case)

You just have to learn and read about it properly. Your loop condition start = 1000 will always evaluate to true, that's why the loop never terminates (an assignment returns the value which was assigned and any other number than 0 is evaluates to true).
The MDN JavaScript Guide is a great resource for learning JavaScript. Particular for this situation:
A for loop repeats until a specified condition evaluates to false. The JavaScript for loop is similar to the Java and C for loop. A for statement looks as follows:
for ([initialExpression]; [condition]; [incrementExpression])
statement
When a for loop executes, the following occurs:
The initializing expression initialExpression, if any, is executed. This expression usually initializes one or more loop counters, but the syntax allows an expression of any degree of complexity. This expression can also declare variables.
The condition expression is evaluated. If the value of condition is true, the loop statements execute. If the value of condition is false, the for loop terminates. If the condition expression is omitted entirely, the condition is assumed to be true.
The statement executes. To execute multiple statements, use a block statement ({ ... }) to group those statements.
The update expression incrementExpression, if there is one, executes, and control returns to step 2.
As the others said, it mostly comes down to try and error.... that is a good way of learning anyway.

your conditional statement start=1000 will always return true. You cant found such fool proof's list for this, you have to learn from these mistakes on your own.

Uh - what did you wanted here ?
for (start = 3; start = 1000; start += 1)
do you wanted this ? ( from 3 to 1000 )
for (start = 3; start <= 1000; start += 1)
in first case you will stuck on 1000