数组是 JS 最常见的一种数据结构, 咱们在开发中也经常用到, 在这篇文章中, 提供一些小技巧, 帮助咱们提高开发效率.
1. 删除数组的重复项
这是一个非常流行的关于 JavaScript 数组的面试问题, 如何从 JavaScript 数组中提取唯一的值. 这里有一个简单快捷的解决方案, 您可以使用一个 new Set() 来解决这个问题. 我想向您展示两种可能的方法, 一种是使用. from() 方法, 另一种是使用 spread 操作符 (...).
- var fruits = ["banana", "apple", "orange", "watermelon", "apple", "orange", "grape", "apple"];
- // First method
- var uniqueFruits = Array.from(new Set(fruits));
- console.log(uniqueFruits); // returns ["banana", "apple", "orange", "watermelon", "grape"]
- // Second method
- var uniqueFruits2 = [...new Set(fruits)];
- console.log(uniqueFruits2); // returns ["banana", "apple", "orange", "watermelon", "grape"]
容易吧?
2. 替换数组中的特定值
有时在创建代码时需要替换数组中的特定值, 有一种很好的简短方法可以做到这一点, 咱们可以使用. splice(start,value to remove,valueToAdd), 这些参数指定咱们希望从哪里开始修改, 修改多少个值和替换新值.
- var fruits = ["banana","apple","orange","watermelon","apple","orange","grape","apple"];
- fruits.splice(0, 2, "potato", "tomato");
- console.log(fruits);
- //returns["potato","tomato","orange","watermelon","apple","orange","grape","apple"]
3. Array.from 达到 .map 的效果
咱们都知道 .map() 方法,.from() 方法也可以用来获得类似的效果且代码也很简洁.
- var friends = [
- { name: 'John', age: 22 },
- { name: 'Peter', age: 23 },
- { name: 'Mark', age: 24 },
- { name: 'Maria', age: 22 },
- { name: 'Monica', age: 21 },
- { name: 'Martha', age: 19 },
- ]
- var friendsNames = Array.from(friends, ({name}) => name);
- console.log(friendsNames);
- //returns["John","Peter","Mark","Maria","Monica","Martha"]
4. 置空数组
有时候我们需要清空数组, 一个快捷的方法就是直接让数组的 length 属性为 0, 就可以清空数组了.
- var fruits = ["banana","apple","orange","watermelon","apple","orange","grape","apple"];
- fruits.length = 0;
- console.log(fruits); // returns []
5. 将数组转换为对象
有时候, 出于某种目的, 需要将数组转化成对象, 一个简单快速的方法是就使用展开运算符号 (...):
- var fruits = ["banana", "apple", "orange", "watermelon"];
- var fruitsObj = {
- ...fruits
- };
- console.log(fruitsObj);
- //returns{
- 0:"banana",1:"apple",2:"orange",3:"watermelon",4:"apple",5:"orange",6:"grape",7:"apple"
- }
6. 用数据填充数组
在某些情况下, 当咱们创建一个数组并希望用一些数据来填充它, 这时 .fill() 方法可以帮助咱们.
- var newArray = new Array(10).fill("1");
- console.log(newArray);
- //returns["1","1","1","1","1","1","1","1","1","1","1"]
7. 数组合并
使用展开操作符, 也可以将多个数组合并起来.
- var fruits = ["apple", "banana", "orange"];
- var meat = ["poultry", "beef", "fish"];
- var vegetables = ["potato", "tomato", "cucumber"];
- var food = [...fruits, ...meat, ...vegetables];
- console.log(food);
- //["apple","banana","orange","poultry","beef","fish","potato","tomato","cucumber"]
8. 求两个数组的交集
求两个数组的交集在面试中也是有一定难度的正点, 为了找到两个数组的交集, 首先使用上面的方法确保所检查数组中的值不重复, 接着使用. filter 方法和. includes 方法. 如下所示:
- var numOne = [0, 2, 4, 6, 8, 8];
- var numTwo = [1, 2, 3, 4, 5, 6];
- var duplicatedValues = [...new Set(numOne)].filter(item => numTwo.includes(item));
- console.log(duplicatedValues); // returns [2, 4, 6]
9. 从数组中删除虚值
在 JS 中, 虚值有 false, 0,'', null, NaN, undefined. 咱们可以 .filter() 方法来过滤这些虚值.
- var mixedArr = [0, "blue", "", NaN, 9, true, undefined,"white", false];
- var trueArr = mixedArr.filter(Boolean);
- console.log(trueArr); // returns ["blue", 9, true, "white"]
10. 从数组中获取随机值
有时我们需要从数组中随机选择一个值. 一种方便的方法是可以根据数组长度获得一个随机索引, 如下所示:
- var colors=["blue","white","green","navy","pink","purple","orange","yellow","black","brown"];
- var randomColor = colors[(Math.floor(Math.random() * (colors.length)))]
11. 反转数组
现在, 咱们需要反转数组时, 没有必要通过复杂的循环和函数来创建它, 数组的 reverse 方法就可以做了:
- var colors = ["blue","white","green","navy","pink","purple","orange","yellow","black","brown"];
- var reversedColors = colors.reverse();
- console.log(reversedColors);
- //returns["brown","black","yellow","orange","purple","pink","navy","green","white","blue"]
12 lastIndexOf() 方法
- var nums = [1, 5, 2, 6, 3, 5, 2, 3, 6, 5, 2, 7];
- var lastIndex = nums.lastIndexOf(5);
- console.log(lastIndex); // returns 9
13. 对数组中的所有值求和
JS 面试中也经常用 reduce 方法来巧妙的解决问题
- var friends = [
- { name: 'John', age: 22 },
- { name: 'Peter', age: 23 },
- { name: 'Mark', age: 24 },
- { name: 'Maria', age: 22 },
- { name: 'Monica', age: 21 },
- { name: 'Martha', age: 19 },
- ]
- var friendsNames = Array.from(friends, ({name}) => name);
- console.log(friendsNames);
- //returns ["John","Peter","Mark","Maria","Monica","Martha"]
总结
在本文中, 介绍了 13 个技巧, 希望它们可以帮助编写简洁代码, 如果你还有更好的办法, 欢迎留言讨论.
来源: http://www.css88.com/web/javascript/14288.html