1. 来吧，开始学习了
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/*
数组变成一个字符串：
1.join() : 可以在每一个元素中加一个字符串
2.toString()
*/
/*
pop(): 删除数组最后一个元素
push(): 增加数组
reverse() : 反转
slice(): 从下标开始取
sort(): 对数组进行排序，
splice(): 删除数组的某几个
toString(): 把数组变成字符串
unshift() : 新增最前面的
split(): 用于把一个字符串分割成字符串数组.
every() : 完全
some(): 不完全,只要有一个满足就行了
filter() : 过滤函数
reduce()
reduceRight():
*/
/**
* 不改变： 1. concat(),是不会改变原数组的
* 2. join()
* 3. slice()
* 4. toString()
* 5. map()
* 6. every()
* 7. some()
* 8. filter()
* 9. reduce()
* 10. reduceRight()
*
* 改变： 1. pop()
* 2. push()
* 3. reverse()
* 4. shift()
* 5. sort()
* 6. splice()
* 7. unshift()
*
* 不确定： forEach，map
*
*/
/* var arr1 = [1, 2, 3]
arr2 = [2, 3, 4]
arr3 = []
arr3 = arr1.concat(arr2)
console.log(arr1)
console.log(arr2)
console.log(arr3) */
/* var arr1 = [1, 2, 3]
res = null;
res = arr1.join(',')
console.log(res)
*/
/*
var arr1 = [1, 2, 3]
res = null;
res = arr1.pop()
console.log(arr1, res)
*/
/* var arr1 = [1, 2, 3]
res = null;
res = arr1.push(4)
console.log(arr1, res) */
/* var arr1 = [1, 2, 3]
res = null;
res = arr1.reverse()
console.log(arr1, res) */
/*
var arr1 = [1, 2, 3]
res = null;
res = arr1.shift()
console.log(arr1, res)
*/
/*
var arr1 = [1, 2, 3, 4, 5, 6]
res = null;
res = arr1.slice(3)
console.log(arr1, res) */
/*
var arr1 = [3, 2, 3, 4, 5, 6]
res = null;
res = arr1.sort()
console.log(arr1, res)
*/
/*
var arr1 = [3, 2, 3, 4, 5, 6]
res = null;
res = arr1.splice(4, 2)
console.log(arr1, res)
*/
/*
var arr1 = [3, 2, 3, 4, 5, 6]
res = null;
res = arr1.toString()
console.log(arr1, res) */
/*
var arr1 = [3, 2, 3, 4, 5, 6];
res = null;
res = arr1.unshift(11);
console.log(arr1, res); */
/*
var arr1 = [3, 2, 3, 4, 5, 6];
res = null;
var str = "2,123,456";
var res = str.split(",");
console.log(str, res);
*/
// 注意❤️：用forEach是不会改变数组里面的值的，不会改变原数组的，forEach是不会改变value里面的值的，要改变的话，只能通过数组改变,forEach是不确定的
/* var arr1 = [3, 2, 3, 4, 5, 6];
res = [];
arr1.forEach(function (value, index) {
// value += 1;
arr1[index] += 1;
});
console.log(arr1); */
/* var arr1 = [3, 2, 3, 4, 5, 6];
res = [];
res = arr1.map(function (value, index) {
return value + 1;
});
console.log(arr1, res); */
/* var arr1 = [{ value: 1 }, { value: 2 }, { value: 3 }];
res = [];
res = arr1.map(function (value, index) {
return value.value;
});
console.log(arr1, res); */
// 引用类型，是指向同一个 地址的
/* var arr1 = [{ value: 1 }, { value: 2 }, { value: 3 }];
res = [];
res = arr1.map(function (value, index) {
value.name = index;
return value;
});
console.log(arr1, res);
*/
/*
var arr1 = [{ value: 1 }, { value: 2 }, { value: 3 }];
res = [];
res = arr1.map(function (value, index, array) {
console.log(value);
console.log(index);
console.log(array);
return value, index, array;
});
console.log(arr1, res); */
/*
map,forEach的区别:
1.forEach是不确定要不要改变原数组的
2.map是需要改变原数组的 ，（return出来新的值，return过后是新的数组了）
3.map是映射函数，把一个数组关联到另一个数组，，，（后端mapping，映射关系，表的关联模型）
4.map是数组扩展的方法
*/
/*
var arr = [1, 2, 3, 4, 5, -6, 7];
res = [];
res = arr.every(function (elem) {
return elem > 0;
});
console.log(arr, res); */
/* var arr = [1, 2, 3, 4, 5, 6, 7];
res = [];
res = arr.some(function (elem) {
return elem < 0;
});
console.log(arr, res); */
/* var arr = [1, 2, 3, 4, 5, -6, 7];
res = [];
res = arr.filter(function (elem) {
return elem > 0;
});
console.log(arr, res); */
/* var arr = [1, 2, 3, 4, 5, -6, 7];
res = [];
res = arr.reduce(function (prev, value) {
prev.push(value + 1);
return prev;
}, res);
console.log(arr, res); */
var arr = [1, 2, 3, 4, 5, -6, 7];
res = [];
res = arr.reduceRight(function (prev, value) {
prev.push(value + 1);
return prev;
}, res);
console.log(arr, res);
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