operators md file

Author: Rebecca Murphey

content/javascript-101/operators.md

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+---
+chapter : "js101"
+section:  "javascript-basics"
+title:    "Operators"
+---
+## Basic Operators
+
+## Basic Operators
+
+Basic operators allow you to manipulate values.
+
+<div class="example" markdown="1">
+Concatenation
+
+  var foo = 'hello';
+  var bar = 'world';
+  console.log(foo + ' ' + bar); // 'hello world'
+</div>
+
+<div class="example" markdown="1">
+Multiplication and division
+
+    2 * 3;
+    2 / 3;
+</div>
+
+<div class="example" markdown="1">
+Incrementing and decrementing
+
+    var i = 1;
+    var j = ++i;  // pre-increment:  j equals 2; i equals 2
+    var k = i++;  // post-increment: k equals 2; i equals 3
+</div>
+
+### Operations on Numbers & Strings
+
+In JavaScript, numbers and strings will occasionally behave in ways you might not expect.
+
+<div class="example" markdown="1">
+Addition vs. concatenation
+
+  var foo = 1;
+  var bar = '2';
+  console.log(foo + bar);  // 12. uh oh
+</div>
+
+<div class="example" markdown="1">
+Forcing a string to act as a number
+
+  var foo = 1;
+  var bar = '2';
+
+  // coerce the string to a number
+  console.log(foo + Number(bar));
+</div>
+
+
+The Number constructor, when called as a function (like above) will have the
+effect of casting its argument into a number. You could also use the unary plus
+operator, which does the same thing:
+
+<div class="example" markdown="1">
+Forcing a string to act as a number (using the unary-plus operator)
+console.log(foo + +bar);
+</div>
+
+### Logical Operators
+
+Logical operators allow you to evaluate a series of operands using AND and OR operations.
+
+<div class="example" markdown="1">
+Logical AND and OR operators
+
+    var foo = 1;
+    var bar = 0;
+    var baz = 2;
+
+    foo || bar;   // returns 1, which is true
+    bar || foo;   // returns 1, which is true
+
+    foo && bar;   // returns 0, which is false
+    foo && baz;   // returns 2, which is true
+    baz && foo;   // returns 1, which is true
+</div>
+
+Though it may not be clear from the example, the || operator returns the value
+of the first truthy operand, or, in cases where neither operand is truthy,
+it'll return the last of both operands. The && operator returns the value of
+the first false operand, or the value of the last operand if both operands are
+truthy.
+
+Be sure to consult the section called “Truthy and Falsy Things” for more
+details on which values evaluate to true and which evaluate to false.
+
+<div class="note">
+## Note
+
+You'll sometimes see developers use these logical operators for flow control
+instead of using if statements. For example:
+
+<div class="example" markdown="1">
+// do something with foo if foo is truthy
+foo && doSomething(foo);
+
+// set bar to baz if baz is truthy;
+// otherwise, set it to the return
+// value of createBar()
+var bar = baz || createBar();
+</div>
+
+This style is quite elegant and pleasantly terse; that said, it can be really
+hard to read, especially for beginners. I bring it up here so you'll recognize
+it in code you read, but I don't recommend using it until you're extremely
+comfortable with what it means and how you can expect it to behave.
+
+### Comparison Operators
+
+Comparison operators allow you to test whether values are equivalent or whether
+values are identical.
+
+<div class="example" markdown="1">
+Comparison operators
+
+    var foo = 1;
+    var bar = 0;
+    var baz = '1';
+    var bim = 2;
+
+    foo == bar;   // returns false
+    foo != bar;   // returns true
+    foo == baz;   // returns true; careful!
+
+    foo === baz;             // returns false
+    foo !== baz;             // returns true
+    foo === parseInt(baz);   // returns true
+
+    foo > bim;    // returns false
+    bim > baz;    // returns true
+    foo <= baz;   // returns true
+</div>