javascript我可以在字符串中放入变量检查

Question

is something like this possible in javascript?

maybe I have a variable (in this case its a number) that sometimes might be undefined. I'd like to sort of do some code right in the string to check the variable...

ps: I know that this throws throws an error!

var mystring='<b class="my string">'+(if(variable){variable;}else{0;})+'</b>';

Answer 1

You can using the conditional operator ( ?: ) :

var
    variable = true,
    mystring = 'Hello, ' + ( variable ? 'world' : 'nobody' ) + '!'
;

JSFiddle demo .

Answer 2

It seems the ternary operator ? will be of some use for you :

var like = true;

var myString = 'some string i ' +  ( (like) ? 'really' : 'do not' ) + ' like' ;

Answer 3

The typeof operator will specifically tell you if the variable is defined or not.

Link: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/typeof

eg

var mystring = 'The variable ' + (typeof variable !== 'undefined' ? 'exists' : 'doesn\'t exist');

JSFiddle: http://jsfiddle.net/FlameTrap/AJfFk/1/

Answer 4

var mystring = '<b class="my string">' + ( typeof variable !== undefined ) ? 'variable' : 0 + '</b>';