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js simple method to determine the length of a string/judgment of empty_javascript skills

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Release： 2016-05-16 17:26:51

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Three methods available for calculating string length:

Copy code The code is as follows:

echo “$str” awk ‘{print length($0)}’ 
expr length “$str” 
echo “$str”wc -c 

But the The values obtained by the three methods will be 1 more, possibly because the terminator is also included in the calculation.
There are three ways to determine whether a string is empty:

Copy code The code is as follows:

if [ "$str" = "" ] 
if [ x"$str" = x ] 
if [ -z "$str" ] 

Note: You must put double quotes, otherwise some commands will report errors, so you should develop a good habit!

Related labels：

Judgment empty character

source：php.cn

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