First of all, the syntax of if expression is:

if (expression) statement

expressionexpressionis executed. If the result istruthy(true value),statementis executed. If it isfalsy(false value), it is not executed.

truthyandfalsyinJavaScript. The false value is

false undefined null 0 -0 NaN "" // the empty string

Except for these, the rest are true values.

Please search for keywords yourself:Implicit type conversion

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This is an if judgment expression. The specific syntax is as follows:

if (condition) statement1 [else statement2]

The value in condition needs to be of Boolean type true or false

In Javascript, the following values will be implicitly converted to false:
0, -0, null, false, NaN, undefined, "" (empty string)
Other values will be converted to true, please note that "false "It's also true.

if (aa)is equivalent to

if (!!aa){ console.log('here goes true'); }