At a high level, an expression is a valid unit of code that resolves to a value. There are two types of expressions: those that have side effects (such as assigning values) and those that purely evaluate.
Example#1: The expression x = 7 uses the
=operator to assign the value seven to the variablex. The expression evaluates to 7.
Example #2: The expression 3 + 4 is an expression that uses the
+operator to add 3 and 4 together and produces a value, 7. However, if it’s not eventually part of a bigger construct (for example, a variable declaration like const z = 3 + 4), its result will be immediately discarded — this is usually a programmer mistake because the evaluation doesn’t produce any effects.
Loops offer a quick and easy way to do something repeatedly. You can think of a loop as a computerized version of the game where you tell someone to take X steps in one direction, then Y steps in another. For example, the idea “Go five steps to the east” could be expressed this way as a loop:
for (let step = 0; step < 5; step++) {Runs 5 times, with values of step 0 through 4. console.log("Walking east one step"); }
If it evaluates to true , the statement or code in the loop is executed. If it evaluates to false , the loop stops.
The while loop starts by evaluating condition . If condition evaluates to true , the code in the code block gets executed. If condition evaluates to false , the code in the code block is not executed and the loop ends
Read