Parsing — Complete Guide
Parsing — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of JavaScript Tutorial on Toolliyo Academy.
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JavaScript Tutorial · Lesson 38 of 100
Parsing
Basics ✓ → Objects & data → Async & DOM → Advanced → Tools → Projects
Intermediate · 2 — Built-in types & objects · ~6 min · JS Strings, Dates & RegEx
What is this?
Parsing means turning strings into numbers, dates, or structured data — Number(), parseInt, JSON.parse, Date parsing.
Why should you care?
Form fields and API text arrive as strings; parsing converts them for logic.
See it live — copy this example
Paste into an HTML file or the browser console (F12). Use Run below when the live editor is available.
console.log(parseInt("42px", 10));
console.log(parseFloat("3.14"));
console.log(Number(" 7 "));Run Example »
Edit the code below and click Run to see the result in Toolliyo’s live editor.
What happened?
- parseInt stops at non-digits (42 from "42px").
- Number trims whitespace.
- Always pass radix 10 to parseInt.
Practice next
- Parse "42px" with parseInt radix 10.
- Use parseFloat on "3.14kg".
- Compare Number(" 7 ") trimming behavior.
- Parse a query string param "page=3" into number 3.
- Safely parse JSON inside try/catch and log parse errors.
Remember
parseInt/parseFloat for partial strings Number for full string Validate with isNaN
ScriptVerse filters
Admin table reads minPrice from URL query, parses to number, and filters products.
Outcome: Robust parsing keeps URL-driven filters from breaking on bad input.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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