javascript基础知识梳理-原始类型

来源：互联网发布：switch case用法 java 编辑：程序博客网时间：2024/05/01 16:20
<!DOCTYPE html><html><head><meta charset="UTF-8"><title>Insert title here</title><script type="text/javascript">//原始类型：string,number,bool,null,undefined//当number+bool时,会将bool的true转换成1,false转换成0,颠倒顺序不影响结果var result = true + 10;console.log("10 + true = " + result);//当number+null时,会将null转换成0做加法,颠倒顺序不影响结果result = 10 + null;console.log("10 + null = " + result);//当number+undefined时,结果是NaN,颠倒顺序不影响结果result = undefined + 10;console.log("10 + undefined = " + result);//当undefined+undefined时,结果是NaNresult = undefined + undefined;console.log("undefined + undefined = " + result);//当undefined+bool时,结果是NaNresult = undefined + true;console.log("undefined + true = " + result);//当undefined+null时,结果是NaN,综上undefined与number,null,bool值做四则运算,结果都是NaNresult = undefined + null;console.log("undefined + null = " + result);//当string+number时,结果是stringresult = "10" + 10;console.log('"10" + 10 = ' + result);//当number+string时,结果还是stringresult = 10 + "10";console.log('10 + "10" = ' + result);//当number*string时,结果就变成了number,如果string无法转换成number,则结果是NaNresult = 10 * "10";console.log('10 * "10" = ' + result);result = 10 * "10g";console.log('10 * "10g" = ' + result);//当undefined&&undefined,值仍然为undefinedresult = undefined && undefined;console.log("undefined && undefined = " + result);//引用类型,对象,数组,函数//当string+object,结果为stringresult = "10" + {};console.log('"10" + {} = ' + result);//当number+object,结果也是stringresult = 10 + {};console.log("10 + {} = " + result);//当number*object,结果为NaN,其实这时候object转换成了一个string,并且该string无法转换成numberresult = 10 * {};console.log("10 * {} = " + result);//原始类型之间的比较result = null == undefined;console.log("null == undefined:" + result);result = null == 0;console.log("null == 0:" + result);result = null == "0";console.log("null == '0':" + result);result = null == false;console.log("null == false:" + result);result = undefined == 0;console.log("undefined == 0:" + result);result = undefined == "0";console.log("undefined == '0':" + result);result = undefined == false;console.log("undefined == false:" + result);result = "0" == 0;console.log("'0' == 0:" + result);result = "0" == false;console.log("'0' == false:" + result);result = 0 == false;console.log("0 == false:" + result);//事实证明,0,'0',false是两两相等的,和null,undefined都不相等,但是null和undefined确是相等的//类型转换函数的使用,Number,String,Boolean,Object</script></head><body></body></html>
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