Conditional Statement in JavaScript

Question

In C#.Net, We would use Conditional Statement like this below:

string Place = TextBox1.Text == "" ? "School" : TextBox1.Text;

How to use Conditional Statement in JavaScript. I am assigning one value to the TextBox, If there is no value then I want to assign "1" to the TextBox.

Here I used like this,

document.getElementById('<%=txtPlace.ClientID %>').value   = obj[1];

If obj[1] == "" then I want to assign "1" to the TextBox. How to assign? It can be done easily by using If statement. But I want to know how to use Conditional Statement in JavaScript? Is there Conditional Statement in JavaScript? If so then how to use it?

Frédéric Hamidi · Accepted Answer · 2011-06-29 12:27:08Z

5

Yes, Javascript does support the conditional operator:

document.getElementById('<%=txtPlace.ClientID %>').value = obj[1] ? obj[1] : "1";

Alternatively, you can take advantage of its short-circuiting logical OR operator:

document.getElementById('<%=txtPlace.ClientID %>').value = obj[1] || "1";

answered Jun 29, 2011 at 12:27

Frédéric Hamidi

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6 Comments

thevan Over a year ago

@Hamidi: thank you for your answer. But I dont have idea about OR operator. Here if we use OR operator what value would be assigned to the TextBox.

Daniel Over a year ago

@thevan, the two lines are equivalent.

thevan Over a year ago

@Daniel: Yes I tried. You are right. thank you so much Daniel.

Frédéric Hamidi Over a year ago

@thevan, if obj[1] is the empty string, it will evaluate to false and the second operand will be evaluated and returned, so the value of the text box will be "1". If obj[1] is a non-empty string, it will evaluate to true, so the second operand won't be evaluated and the value of the text box will be the string stored in obj[1].

brymck Over a year ago

obj[1] || "1" means that if obj[1] is truthy -- i.e. anything but false, null, undefined, 0, "", NaN -- the OR statement will stop and return obj[1]. Otherwise, it will continue on to "1" and return that. The term short-circuit is used because once part of a || b || c || d evaluates to a truthy value, it stops and equals that value.

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dcp · Accepted Answer · 2011-06-29 12:25:03Z

3

Yes, there is conditional statement in javascript, it works the same way:

document.getElementById('<%=txtPlace.ClientID %>').value = obj[1] === "" ? "1" : obj[1];

answered Jun 29, 2011 at 12:25

dcp

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Comments

FishBasketGordo · Accepted Answer · 2011-06-29 12:26:57Z

1

The conditional (or ternary) operator is the same in JavaScript:

condition ? true-value : false-value

So your code would look like this:

document.getElementById('<%=txtPlace.ClientID %>').value = obj[1] === "" ? "1" : obj[1];

answered Jun 29, 2011 at 12:26

FishBasketGordo

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Comments

Mathias Schwarz · Accepted Answer · 2011-06-29 12:27:10Z

1

Yes, there is and it behaves in the same way as in C#.

document.getElementById('<%=txtPlace.ClientID %>').value = obj[1]==""?"1":"something";

answered Jun 29, 2011 at 12:27

Mathias Schwarz

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