Explain the purpose of using the 'let {}' construct in programming language.

In Kotlin, the let {} construct is an extension function that is applied to an object and allows executing a block of code with that object as an argument (usually denoted as it). It is often used for:

• Avoiding explicit null checks (in combination with safe call ?.let {})
• Locally limiting the scope of a variable
• Simplifying chains of calls

Example of usage with null check:

val name: String? = "Kotlin"
name?.let {
    println("String length: ${it.length}")
}

Here, the code inside let executes only if name is not null.

Example for limiting scope:

val result = someObject.let {
    // you can work with it as someObject
    it.property + 10
}

Thus, let helps write cleaner and safer code.