js数组里面放键值对

今天，我们来一起学习一下如何把元素添加到元素的首个元素。

1.Array.unshift()

letfruits=["Apple","Banana","Mango"];fruits.unshift("Orange");console.log(fruits);//Prints["Orange","Apple","Banana","Mango"]fruits.unshift("Guava","Papaya");console.log(fruits);//Prints["Guava","Papaya","Orange","Apple","Banana","Mango"]

2.使用展开运算符(…)

varfruits=["Apple","Banana","Mango"];varmoreFruits=["Orange",...fruits];console.log(moreFruits);//Prints["Orange","Apple","Banana","Mango"]varsomeoMoreFruits=["Guava","Papaya",...moreFruits];console.log(someoMoreFruits);//Prints["Guava","Papaya","Orange","Apple","Banana","Mango"]console.log(fruits);//Prints["Apple","Banana","Mango"]

3.使用 Array.ｃｏｎｃａｔ()

我们还可以使用ｃｏｎｃａｔ()方法在开头连接两个(或更多)数组。

varfruits=["Apple","Banana","Mango"];varmoreFruits=["Orange"];varsomeoMoreFruits=["Guava","Papaya"];varallFruits=someoMoreFruits.ｃｏｎｃａｔ(moreFruits,fruits);console.log(allFruits);//Prints["Guava","Papaya","Orange","Apple","Banana","Mango"]

完~我是小智，我要去刷碗了，我们下期再见~

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