An expression in JavaScript is a combination of values, variables, operators, and functions that the JavaScript engine can evaluate and produce a result. Expressions can be used to assign values to variables, compare values, perform arithmetic operations, and more.
A loop in JavaScript is a programming structure that allows you to repeat a block of code multiple times. We use loops in our code when we need to perform a specific action multiple times, such as iterating over an array or processing a set of data.
A for loop in JavaScript stops executing when the condition specified in the loop header evaluates to false. The loop header consists of three parts: initialization, condition, and update. The initialization part is executed only once at the beginning of the loop, the condition is checked before each iteration, and the update part is executed after each iteration. When the condition evaluates to false, the loop stops executing.
A while loop in JavaScript executes as long as the condition specified in the loop header evaluates to true. The loop header consists of a single condition. The loop will execute as many times as it takes for the condition to evaluate to false. It is possible for a while loop to execute zero times if the condition is initially false.