目標

今天要來學習的是陣列操作，包含some(), every(), find(), findIndex(), splice()

範例資料

const people = [
    { name: 'Wes', year: 1988 },
    { name: 'Kait', year: 1986 },
    { name: 'Irv', year: 1970 },
    { name: 'Lux', year: 2015 }
];

const comments = [
    { text: 'Love this!', id: 523423 },
    { text: 'Super good', id: 823423 },
    { text: 'You are the best', id: 2039842 },
    { text: 'Ramen is my fav food ever', id: 123523 },
    { text: 'Nice Nice Nice!', id: 542328 }
];

some()

//複雜
const isAdult = people.some(function (person) {
	const currentYear = (new Date()).getFullYear();
	if (currentYear - person.year >= 19) {
	    return true;
	}
});
//簡化
const is_adult = people.some(persion => {
	const currentYear = (new Date()).getFullYear();
	return currentYear - persion.year >= 19;
});
//極簡   
const is_adult = people.some(persion => (new Date()).getFullYear() - persion.year >= 19);

Array.prototype.some() 透過給定函式、測試陣列中是否至少有一個元素，通過該函式所實作的測試，這方法回傳的是布林值

every()

const is_adult = people.every(persion => (new Date()).getFullYear() - persion.year >= 19);

Array.prototype.every()測試陣列中的所有元素是否都通過了由給定之函式所實作的測試，這方法回傳的是布林值

find()

const comment = comments.find(function (comment) {
  if(comment.id === 823423) {
    return true;
  }
});
//極簡
const comment = comments.find(comment => comment.id === 823423);

Array.prototype.find()回傳第一個滿足所提供之測試函式的元素值

findIndex()

// Find the comment with this ID
// delete the comment with the ID of 823423
const index = comments.findIndex(comment => comment.id === 823423);

Array.prototype.findIndex()依據提供的測試函式，尋找陣列中符合的元素，並返回其 index（索引）

splice()

移除陣列內容

comments.splice(index, 1);

splice() 可以藉由刪除既有元素並／或加入新元素來改變一個陣列的內容

redux

//redux
const newComments = [
    ...comments.slice(0, index),
    ...comments.slice(index + 1)
];

這是另外一種方法，是透過建立一個新陣列達成