Using for directive in Blockchain / Solidity - Step-by-Step Execution

Concept Flow - Using for directive

Start

↓

Initialize loop variable

↓

Check loop condition

| Yes↓

Execute loop body

↓

Update loop variable

↓

Check loop condition

No↓

End loop

The for directive starts by setting a variable, checks a condition, runs the loop body if true, updates the variable, and repeats until the condition is false.

Execution Sample

Blockchain / Solidity

for (let i = 0; i < 3; i++) {
  console.log(i);
}

This code prints numbers 0, 1, and 2 using a for loop.

Execution Table

Iteration	i	Condition i < 3	Action	Output
1	0	true	Print i=0	0
2	1	true	Print i=1	1
3	2	true	Print i=2	2
4	3	false	Exit loop

💡 i reaches 3, condition i < 3 is false, loop ends

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
i	0	1	2	3	3

Key Moments - 2 Insights

Why does the loop stop when i equals 3?

Because the condition i < 3 becomes false at iteration 4 (see execution_table row 4), so the loop exits.

When is the loop variable i updated?

After executing the loop body in each iteration, i is increased by 1 before the next condition check (see variable_tracker changes).

Visual Quiz - 3 Questions

Look at the execution table, what is the value of i during the third iteration?

A 2

B 3

C 1

D 0

💡 Hint

Check the 'i' column in the execution_table at iteration 3.

At which iteration does the loop condition become false?

A Iteration 3

B Iteration 2

C Iteration 4

D Iteration 1

💡 Hint

Look at the 'Condition i < 3' column in the execution_table.

If the loop condition changed to i <= 3, how many times would the loop run?

A 3 times

B 4 times

C 2 times

D 5 times

💡 Hint

Think about when i <= 3 is true based on variable_tracker values.

Concept Snapshot

for directive syntax:
for (initialization; condition; update) {
  // code to repeat
}

- Initialize variable once
- Check condition before each loop
- Run code if true
- Update variable after each loop
- Repeat until condition false

Full Transcript

The for directive runs a loop by first setting a variable, then checking if it meets a condition. If yes, it runs the loop body, then updates the variable. This repeats until the condition is false, then the loop stops. For example, a loop from 0 to 2 prints 0, 1, 2. The variable i starts at 0 and increases by 1 each time. When i reaches 3, the condition fails and the loop ends.