How to get the largest element in a Number type array
This time I will show you how to get the largest element in the Number type array, and what are the precautions for getting the largest element in the Number type array. The following is a practical case, let's take a look.
1. Do not use any library function
The code is as follows:function findMax1 (arr) {
let result = 0;
if (Array.isArray(arr)) {
for (let i = 0; i < arr.length; i++) {
result = arr[i] > result ? arr[i] : result;
}
return result;
} else {
console.error('The parameter arr is not an array');
return;
}
}2. Use Array.reduce()
The code is as follows:function findMax2 (arr) {
let result = 0;
if (Array.isArray(arr)) {
result = arr.reduce((a, b) => {
return a > b ? a : b;
}, 0);
return result;
} else {
console.error('The parameter arr is not an array');
return;
}
}- accumulator: Accumulator, which is the result of the last callback run. If initialValue is provided, then the first time is initialValue;
- currentValue: the elements of the currently traversed array;
- currentIndex: the currently traversed The index of the array element, starting from 0. If initialValue is provided, it starts from 1;
- array: the array to which reduce is currently applied.
3. Use Apply and Math.max()
The code is as follows:function findMax3 (arr) {
let result = 0;
if (Array.isArray(arr)) {
result = Math.max.apply(null, arr);
return result;
} else {
console.error('The parameter arr is not an array');
return;
}
}4. Only use Math.max()
The code is as follows:function findMax4 (arr) {
let result = 0;
if (Array.isArray(arr)) {
result = Math.max(...arr);
return result;
} else {
console.error('The parameter arr is not an array');
return;
}
}Math objectCommonly used methods:
ceil round upfloor() round down random() random number method // The pseudo-random number generated is between 0 and 1 (including 0, excluding 1), round rounding3 ,Array arrayObject:
Method to create an array 1:var variable name = new Array(); Create an array with a length of 0. Method 2: var variable name = new Array(length) creates an array object of specified length. Method 3: var variable name = new Array("Element 1", "Element 2"...); Create an array object by specifying elements in the array. Method 4:var 变量名 = ["元素1","元素2"...];
数组要注意的细节：
1. 在javascript中数组的长度是可以发生变化的。
var arr = new Array(); //创建了一个长度为0的数组对象。
arr[100] = 10;
document.write("arr长度："+arr.length+"<br/>");
var arr2 = new Array("狗娃","狗剩","铁蛋");
arr2 = ["狗娃","狗剩","铁蛋","张三"];
document.write("arr2长度："+arr2.length+"<br/>");3.1数字的方法
a、concat把arr1与arr2的数组元素组成一个新的数组返回。 arr1 = arr1.concat(arr2);
b、join使用指定的分隔符把数组中的元素拼装成一个字符串返回。
var elements = arr1.join(",");c、pop ：移除数组中的最后一个元素并返回该元素。
d、push：将新元素添加到一个数组中，并返回数组的新长度值。
arr1.push("你好");e、reverse(); 翻转数组的元素
f、slice指定数组 的开始索引值与结束索引值截取数组的元素，并且返回子数组。（包头不包尾）
var subArr = arr1.slice(1,2);
g、sort排序，排序的时候一定要传入排序的方法。（不传时默认是按照ASCII表排列）
arr1 = [19,1,20,5];
arr1.sort(sortNumber); //排序，排序的时候一定要传入排序的方法。
function sortNumber(num1,num2){
return num1-num2;
}h、splice第一个参数是开始删除元素的 索引值， 第二参数是删除元素的个数，往后的数据就是插入的元素（也可以不写）。
arr1.splice(1,1,"张三","李四","王五");
相信看了本文案例你已经掌握了方法，更多精彩请关注php中文网其它相关文章！
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