Strings and Numbers
Format text, parse numeric input, round deliberately, and avoid floating-point surprises.
Strings and numbers appear at every system boundary. Normalize them early and format them close to the interface.
Work with text
text.js
const raw = " JavaScript Course ";
const title = raw.trim();
console.log(title.toLowerCase().includes("script"));
console.log(title.slice(0, 10));
console.log(`Now learning: ${title}`);
Strings are immutable: methods return new values. Use replaceAll, split, startsWith, and endsWith when they express the transformation clearly.
Parse and format numbers
numbers.js
const minutes = Number("112");
if (!Number.isFinite(minutes)) throw new TypeError("minutes must be numeric");
const hours = Math.floor(minutes / 60);
const remainder = minutes % 60;
console.log(`${hours}h ${remainder}m`);
Binary floating point cannot represent every decimal exactly. Compare calculated decimals with a tolerance, and store money as integer minor units or use a purpose-built decimal type.
Keep this
Trim and validate boundary input, treat strings as immutable, check numeric finiteness, and format for the learner's locale.
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