check if javascript code example

Example 1: javascript check if variable exists

if (typeof myVar !== 'undefined') {
    // myVar is defined
}

Example 2: javascript is variable a string

if (typeof myVar === 'string'){
    //I am indeed a string
}

Example 3: js check if variable is string

if (typeof myVar === 'integer'){
    //I am indeed an integer
}

if (typeof myVar === 'boolean'){
    //I am indeed a boolean
}