Task List Utilities
You are writing helper functions for a task list. Each helper should return a result without mutating the original tasks array.
Write these functions:
addTask(tasks, title) should return a new array with a new incomplete task added.
completeTask(tasks, taskId) should return a new array where only the matching task is completed.
removeTask(tasks, taskId) should return a new array without the matching task.
countIncompleteTasks(tasks) should return the number of incomplete tasks.
Sample checks:
const tasks = [ { id: 1, title: 'Review variables', completed: true }, { id: 2, title: 'Practice functions', completed: false },];const withNewTask = addTask(tasks, 'Build task utilities');console.log(withNewTask.map((task) => task.title));const completed = completeTask(withNewTask, 2);console.log(countIncompleteTasks(completed));console.log(removeTask(completed, 1).map((task) => task.id));console.log(tasks.length);console.log(countIncompleteTasks(tasks));
Expected output:
["Review variables", "Practice functions", "Build task utilities"]1[2, 3]21
The original tasks array should still have two items after these helper functions run.
Solution
Solution:
function addTask(tasks, title) { const ids = tasks.map((task) => task.id); const nextId = Math.max(...ids) + 1; const newTask = { id: nextId, title, completed: false }; return [...tasks, newTask];}function completeTask(tasks, taskId) { return tasks.map((task) => { if (task.id !== taskId) { return task; } return { ...task, completed: true }; });}function removeTask(tasks, taskId) { return tasks.filter((task) => task.id !== taskId);}function countIncompleteTasks(tasks) { return tasks.filter((task) => task.completed === false).length;}const tasks = [ { id: 1, title: 'Review variables', completed: true }, { id: 2, title: 'Practice functions', completed: false },];const withNewTask = addTask(tasks, 'Build task utilities');console.log(withNewTask.map((task) => task.title));const completed = completeTask(withNewTask, 2);console.log(countIncompleteTasks(completed));console.log(removeTask(completed, 1).map((task) => task.id));console.log(tasks.length);console.log(countIncompleteTasks(tasks));
