The JavaScript exception "missing ; before statement" occurs when there is a semicolon (
;
) missing somewhere and can't be added by
automatic semicolon insertion (ASI)
. You need to provide a semicolon, so that JavaScript can parse the source code correctly.
SyntaxError: Expected ';' (Edge) SyntaxError: missing ; before statement (Firefox)
There is a semicolon (
;
) missing somewhere.
JavaScript statements
must be terminated with semicolons. Some of them are affected by
automatic semicolon insertion (ASI)
, but in this case you need to provide a semicolon, so that JavaScript can parse the source code correctly.
However, oftentimes, this error is only a consequence of another error, like not escaping strings properly, or using
var
wrongly. You might also have too many parenthesis somewhere. Carefully check the syntax when this error is thrown.
This error can occur easily when not escaping strings properly and the JavaScript engine is expecting the end of your string already. For example:
var foo = 'Tom's bar'; // SyntaxError: missing ; before statement
You can use double quotes, or escape the apostrophe:
var foo = "Tom's bar"; var foo = 'Tom\'s bar';
You
cannot
declare properties of an object or array with a
var
declaration.
var obj = {};
var obj.foo = 'hi'; // SyntaxError missing ; before statement
var array = [];
var array[0] = 'there'; // SyntaxError missing ; before statement
Instead, omit the
var
keyword:
var obj = {};
obj.foo = 'hi';
var array = [];
array[0] = 'there';
If you come from another programming language, it is also common to use keywords that don't mean the same or have no meaning at all in javaScript:
def print(info){
console.log(info);
}; // SyntaxError missing ; before statement
Instead, use
function
而不是
def
:
function print(info){
console.log(info);
};