【学习笔记--前端-js】Array

var carTypes = ["小型汽车","大型汽车","摩托车"];
console.log(carTypes.length);


var arr1=["arr1Elem0","arr1Elem1"];
var arr2=["arr2Elem0"];
var arr3=["arr3Elem0","arr3Elem1"];
//1.合并数组
console.log(arr1.concat(arr2,arr3));

//2.1在数组中查找元素，并返回对应下标(不存在则返回-1)
console.log(carTypes.indexOf("大型汽车"));

var ages = [15, 16, 18, 10];
function conditionFunc(age){
    return age >= 18;
}
//2.2返回第一个满足条件的元素下标
console.log(ages.findIndex(conditionFunc));


function preDealFunc(item, index, arr){
    if(item.bandingTime != undefined){
        arr[index].bandingTime = item.bandingTime.slice(0,4)+"-"
                                 + item.bandingTime.slice(4,6)+"-"
                                 + item.bandingTime.slice(6,8)+" "
                                 + item.bandingTime.slice(8,10)+":"
                                 + item.bandingTime.slice(10,12);
    }
}
var carInfos = [{plate:"粤A00000", bandingTime:"202004061725"},{plate:"粤B00000", bandingTime:"202004051725"}];
//3.1 对数组的每一个元素执行一遍回调函数。
carInfos.forEach(preDealFunc);
console.table(carInfos);

//3.2 对数组中每个元素执行一次回调函数，将结果放到新的数组中。
var orgNums = [4,-1,0,-4,2];
var absNums = orgNums.map(Math.abs);
console.table(orgNums);
console.table(absNums);

//4.Array.from();将拥有length属性的对象(String)或可迭代对象(Map、Set)转换为Array对象。
//4.1 实际应用一: 处理 NodeList对象
// let ps = document.querySelectorAll('p');
// Array.from(ps).forEach(function (p) {
//   console.log(p);
// });

//4.2 实际应用二: 处理arguments对象
function floatSum() {
  var args = Array.from(arguments);
  let sum = 0.0;
  args.forEach((item, index, arr)=>{
    let tmp = parseFloat(item);
    if(!isNaN(tmp)){
        sum += tmp;
    }
  });
  return sum;
}

console.log(floatSum(2.1,2.0,'o'));

var strArr = ["0","1","2","3","4","5"];
//5. 将数组用指定的分隔符拼接成字符串
console.log(strArr.join(""));
//6. 将数组转换成字符串
console.log(strArr.toString());