js判断数据类型（如数组）及数组操作函数

蔚落 2021-09-23 12:36 431阅读 0赞

在ES5的时候，js数据类型有6种：Number、String、Boolean、undefined、object、Null。

注：[https://blog.csdn.net/u013592575/article/details/95087953][https_blog.csdn.net_u013592575_article_details_95087953]

一、js判断类型

Object.prototype.toString可以看出一个值到底是什么类型。

Object.prototype.toString.call(2) // "[object Number]"
    Object.prototype.toString.call('') // "[object String]"
    Object.prototype.toString.call(true) // "[object Boolean]"
    Object.prototype.toString.call(undefined) // "[object Undefined]"
    Object.prototype.toString.call(null) // "[object Null]"
    Object.prototype.toString.call(Math) // "[object Math]"
    Object.prototype.toString.call({}) // "[object Object]"
    Object.prototype.toString.call([]) // "[object Array]"

注：[https://segmentfault.com/a/1190000013243913][https_segmentfault.com_a_1190000013243913]

二、数组函数

[https://www.jianshu.com/p/66b04163948b][https_www.jianshu.com_p_66b04163948b]

[https://juejin.im/post/5b0903b26fb9a07a9d70c7e0][https_juejin.im_post_5b0903b26fb9a07a9d70c7e0]

三、函数返回数组

function createFunction(){
    
    		    var result = new Array();
    
    		    for (var i = 0; i < 10; i++) {
    
    		        result.push(i)
    
    		    }
    
    		    return result;
    
    		}
    console.log(createFunction());

[http://www.imooc.com/wenda/detail/464877][http_www.imooc.com_wenda_detail_464877]

[https://wangdoc.com/javascript/types/array.html\#forin-%E5%BE%AA%E7%8E%AF%E5%92%8C%E6%95%B0%E7%BB%84%E7%9A%84%E9%81%8D%E5%8E%86][https_wangdoc.com_javascript_types_array.html_forin-_E5_BE_AA_E7_8E_AF_E5_92_8C_E6_95_B0_E7_BB_84_E7_9A_84_E9_81_8D_E5_8E_86]

四、数组元素的字符串化

join()方法是一个非常实用的方法，它把当前Array的每个元素都用指定的字符串连接起来，然后返回连接后的字符串

arrayObj.join(separator); //返回字符串，这个字符串将数组的每一个元素值连接在一起，中间用 separator 隔开。
    
    var arr = ['A', 'B', 'C', 1, 2, 3];
    arr.join('-'); // 'A-B-C-1-2-3'

[https://www.jianshu.com/p/66b04163948b][https_www.jianshu.com_p_66b04163948b]

五、js取json对象的键和值

//构建一个json对象  
    
    var jb={"美的":49,"三星":35,"海信":25,"格力":16,"方太":14};  
    
    for(var key in jb){  
    
      alert(key); //json对象的key  
    
      alert(jb[key]); //json对象的值  
    
    }

[https://www.cnblogs.com/jpfss/p/9687128.html][https_www.cnblogs.com_jpfss_p_9687128.html]

六、js数组去重

function unique (arr) {
    			  return Array.from(new Set(arr))
    			}
    		
    		var arr = [1,1,'true','true',true,true,15,15,false,false, undefined,undefined, null,null, NaN, NaN,'NaN', 0, 0, 'a', 'a',{},{}];
    		console.log(unique(arr));

[https://segmentfault.com/a/1190000016418021?utm\_source=tag-newest][https_segmentfault.com_a_1190000016418021_utm_source_tag-newest]

七、$.each()是对数组的遍历

var arr1=['aa','bb','cc','dd'];
    $.each(arr1,function(i,val){ //两个参数，第一个参数表示遍历的数组的下标，第二个参数表示下标对应的值
    	 console.log(i+'```````'+val);
    });

注：[https://www.cnblogs.com/zhaixr/p/7069857.html][https_www.cnblogs.com_zhaixr_p_7069857.html]

[https_blog.csdn.net_u013592575_article_details_95087953]: https://blog.csdn.net/u013592575/article/details/95087953
[https_segmentfault.com_a_1190000013243913]: https://segmentfault.com/a/1190000013243913
[https_www.jianshu.com_p_66b04163948b]: https://www.jianshu.com/p/66b04163948b
[https_juejin.im_post_5b0903b26fb9a07a9d70c7e0]: https://juejin.im/post/5b0903b26fb9a07a9d70c7e0
[http_www.imooc.com_wenda_detail_464877]: http://www.imooc.com/wenda/detail/464877
[https_wangdoc.com_javascript_types_array.html_forin-_E5_BE_AA_E7_8E_AF_E5_92_8C_E6_95_B0_E7_BB_84_E7_9A_84_E9_81_8D_E5_8E_86]: https://wangdoc.com/javascript/types/array.html#forin-%E5%BE%AA%E7%8E%AF%E5%92%8C%E6%95%B0%E7%BB%84%E7%9A%84%E9%81%8D%E5%8E%86
[https_www.cnblogs.com_jpfss_p_9687128.html]: https://www.cnblogs.com/jpfss/p/9687128.html
[https_segmentfault.com_a_1190000016418021_utm_source_tag-newest]: https://segmentfault.com/a/1190000016418021?utm_source=tag-newest
[https_www.cnblogs.com_zhaixr_p_7069857.html]: https://www.cnblogs.com/zhaixr/p/7069857.html