This doesn't make sense to me, but I have a feeling I saw a code using this:
var abc = def || ghi;
My question is, is this valid? Can we add a condition to a variable declaration? I imagine the answer is no but I have this at the back of my mind that I saw something similar in code once.
An if-then statement can be used to create a new variable for a selected subset of the observations. For each observation in the data set, SAS evaluates the expression following the if. When the expression is true, the statement following then is executed.
To declare a condition variable, use type cond_t. To initialize it, use function cond_init(). Note that all condition variable related names start with cond_. Function cond_init() takes three arguments.
You declare a variable to specify its name and characteristics. The declaration statement for variables is the Dim Statement. Its location and contents determine the variable's characteristics. For variable naming rules and considerations, see Declared Element Names.
Variable Declaration in C You will use the keyword extern to declare a variable at any place. Though you can declare a variable multiple times in your C program, it can be defined only once in a file, a function, or a block of code.
This gives to abc
the value of def
if it isn't falsy (i.e. not false
, null
, undefined
, 0
or an empty string), or the value of ghi
if not.
This is equivalent to:
var abc;
if (def) abc = def;
else abc = ghi;
This is commonly used for options:
function myfunc (opts) {
var mything = opts.mything || "aaa";
}
If you call myfunc({mything:"bbb"})
it uses the value you give. It uses "aaa"
if you provide nothing.
In this case, in order to let the caller wholly skip the parameter, we could also have started the function with
opts = opts || {};
The code var abc = def || ghi;
is the same thing as
if (def) { //where def is a truthy value
var abc = def;
} else {
abc = ghi;
}
You want a condition like an if statement?
if (xxx==="apple") {
var abc = def;
} else {
abc = ghi;
}
which as written as a ternary operator is:
var abc = (xxx==="apple") ? def : ghi;
Yes, you can add condition to variable declaration
You can use it like this,
function greet(person) {
var name = person || 'anonymouse';
alert('Hello ' + name);
}
greet('jashwant');
greet();
jsfiddle demo
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