1. Empty pattern
An empty pattern is considered found at index 0.
if (pattern.length === 0) return 0Typorithm · easy
Naive String Search
▷ Interactive algorithm labnaive-string-searchsearchstringpatternnested-loops
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Full lesson · 8 learning steps Open any exercise for focused practice
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Step 1 of 8 · intro card
Learn Naive String Search
Search Algorithms
Naive String Search tries the pattern at every possible text position and compares characters one by one.
Naive String Search is the simplest substring search.
The outer loop chooses a possible start index in the text.
The inner loop compares pattern characters against text characters.
A full pattern match returns the start index; otherwise the search continues.
Preparing algorithm lab…
01
Try every valid start position.
02
Compare characters from pattern index 0.
03
Stop inner loop on mismatch.
04
Return start index on full match.
05
Worst-case time is O(n * m).
function naiveStringSearch(text, pattern) {
if (pattern.length === 0) return 0;
for (let i = 0; i <= text.length - pattern.length; i++) {
let j = 0;
while (j < pattern.length && text[i + j] === pattern[j]) {
j++;
}
if (j === pattern.length) return i;
}
return -1;
}Read the implementation
Connect each part of the code to the concept before you type.
2. Start positions
Try every start index where the full pattern can fit.
for (let i = 0; i <= text.length - pattern.length; i++)3. Pattern pointer
j tracks how many pattern characters match.
let j = 04. Compare characters
Keep matching while characters agree.
while (j < pattern.length && text[i + j] === pattern[j])5. Advance pattern
Move to the next pattern character after a match.
j++6. Full match
If all pattern characters matched, return the start index.
if (j === pattern.length) return iA complete learning loop
01
Understand
Read the concept map and follow the code breakdown.
02
Reconstruct
Type the implementation, repair mistakes and work through every recall exercise.
03
Verify
Use the final check without hints; revisit weak concepts in short practice sessions.