while

Control structure that creates a loop.

        
          
          while (condition) {  //body of the loop}
          while (condition) {
  //body of the loop
}

        
        
          
            
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Example of printing the squares of numbers from an array:

        
          
          const numbers = [1, 2, 3, 4, 5]let i = 0while (i < numbers.length) {  const currentElement = numbers[i]  console.log(currentElement * currentElement)  i++}// prints 1, 4, 9, 16, 25let count = numbers.lengthwhile (count) {  // option with typecasting in the loop condition  console.log(count)  count--}// prints 5, 4, 3, 2, 1
          const numbers = [1, 2, 3, 4, 5]
let i = 0
while (i < numbers.length) {
  const currentElement = numbers[i]
  console.log(currentElement * currentElement)
  i++
}
// prints 1, 4, 9, 16, 25

let count = numbers.length
while (count) {
  // option with typecasting in the loop condition
  console.log(count)
  count--
}
// prints 5, 4, 3, 2, 1

        
        
          
            
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In practice

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Advice 1

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🛠 Always use alternatives to the while loop that are better suited for the task. For example, arrays have many convenient methods: forEach(), filter(), map(). They are more readable and contain less code.

🛠 Ensure that the condition changes with each execution of the loop body. If this does not happen, then the loop will most likely be infinite.

🛠 while is a more flexible loop than for, but it is easy to make a mistake when writing it. The moment of initialization and modification of variables in for (initialization operation and step) is predefined. They can be violated, but it will not be easy to read. while provides complete freedom to organize the loop as desired; it is completely manual control. It's easy to forget to write something — most often, the variable in the condition is forgotten to be changed in the loop body.

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