JavaScript常用

打印日志

console.log

类型判断

第一种方式
var type = Object.prototype.toString.call(list);
console.log(type);
第二种方式
typeof list == 'string'
第三种方式 注意有3个等号
typeof(list) === 'number'

https://www.codewars.com/kata/last/train/javascript

function last(list)
{
    console.log(arguments);
    console.log(list);
    if(arguments.length==1)
    {
        var type = Object.prototype.toString.call(list);
        console.log(type);
         if(type=='[object Number]')
         {
             return list;
         }
         return list[list.length-1];
    }
    return arguments[arguments.length-1];
}

replace

https://www.codewars.com/kata/remove-exclamation-marks/train/javascript

function removeExclamationMarks(s)
{
    return s.replace(/!/g,'');
}

正则表达式中/i,/g,/ig,/gi,/m的区别和含义

/i (忽略大小写)
/g (全文查找出现的所有匹配字符)
/m (多行查找)
/gi(全文查找、忽略大小写)
/ig(全文查找、忽略大小写)

http://www.w3school.com.cn/jsref/jsref_replace.asp

fromCharCode

function getChar(c)
{
    return String.fromCharCode(c);
}

http://www.w3school.com.cn/jsref/jsref_fromCharCode.asp

for循环遍历数组

function invert(array)
{
    for (var item in array)
    {
        if(array[item]!=0)
        {
            array[item] = array[item] * -1;
        }
    }
    return array;
}

JavaScript居然有-0

function invert(array)
{
    var b = [];
    for (var item in array)
    {
        if(array[item]!=0)
        {
            b.push(-array[item]);
        }
        else
        {
            b.push(0);
        }
    }
    return b;
}

function invert(array) { return array.map(i => i==0 ? 0 : -i); }

向下取整的话，Math.floor(1.6);

https://www.w3schools.com/jsref/jsref_floor.asp

forEach

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach

var array1 = ['a', 'b', 'c'];

array1.forEach(function(element) {
  console.log(element);
});

使用的软件为WebStorm

WebStorm 2016.1.1
Build #WS-145.597, built on March 30, 2016
JRE: 1.8.0_60-b27 x86
JVM: Java HotSpot(TM) Server VM by Oracle Corporation