JavaScript interview questions from qq_javascript skills-JS Tutorial-php.cn

JavaScript interview questions from qq_javascript skills

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Release： 2016-05-16 18:22:25

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Copy code The code is as follows:

 
var info="Tencent Paipai.com (www.paipai.com) It is a well-known e-commerce website owned by Tencent. "; 
info ="Paipai.com was launched on September 12, 2005."; 
info ="It was officially launched on March 13, 2006."; 
info ="It is currently the second largest e-commerce platform in China."; 
info=info.split(","); 
for(var i=0; i{ 
alert(info[i]); 
} 

This question seems like a toss-up at first, because later you have to separate each item with a comma and then alert each item. Why not construct an array? Object to store text content, and a temporary variable info is used to store
such as var info=["Tencent Paipai.com (www.paipai.com) is a well-known e-commerce website under Tencent.","Paipai.com in It was launched online on September 12, 2005, and officially launched on March 13, 2006. It is currently the second largest e-commerce platform in China. But then I thought that if it was optimization, this question would be meaningless.
Look carefully at the info variable and find that it adds a string every time. If the string is large and numerous, it will greatly affect the performance.

The string type in js is a basic type, so generally they are stored on the stack. If the string is large, info will become a very long string each time, which will be very slow

It would be much better if it is stored in a reference type array, such as

Copy code The code is as follows:

 
var temp=[]; 
temp.push("Tencent Paipai (www.paipai) .com) is a well-known e-commerce website owned by Tencent. "); 
temp.push()....//temp is just a pointer to an array on the heap 
.... 

The last trick is temp.join(""). This idea can be adopted for dealing with large string connection problems.