Day 8 of 100: Arrays — Storing and Slicing Test Data

Day 8 of 100 — 100 Days of Playwright with TypeScript Challenge. Phase: JavaScript Fundamentals. JavaScript (Days 1-33) → TypeScript (Days 34-63) → Playwright (Days 64-96) → AI Framework Capstone (Days 97-100).

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Arrays hold test cases, expected values, retrieved rows. Core operations today, power methods tomorrow.

Creating and Accessing

const browsers = ['chromium', 'firefox', 'webkit'];
browsers[0];          // 'chromium'
browsers.length;      // 3
browsers.at(-1);      // 'webkit' — last element
browsers.includes('firefox'); // true

Adding and Removing

const results = [];
results.push('pass');        // add to end
results.unshift('setup-ok'); // add to start
const last = results.pop();  // remove from end
results.indexOf('setup-ok'); // 0

Slicing Without Mutation

const tests = ['t1', 't2', 't3', 't4', 't5'];
const firstTwo = tests.slice(0, 2);  // ['t1','t2'] — original untouched
const shard = tests.slice(2);        // ['t3','t4','t5']

// splice MUTATES — avoid in test code
// tests.splice(1, 2) changes the original array

QA Pattern: Collecting Failures

const failures = [];
for (const tc of [{id:1,ok:true},{id:2,ok:false},{id:3,ok:false}]) {
  if (!tc.ok) failures.push(tc.id);
}
console.log('Failed: ' + failures.join(', ')); // Failed: 2, 3

Tomorrow (Day 9): Array power methods — map, filter, reduce, find.