I need to perform a simple check to see if a given variable is greater than or equal to 0.
public print(value: any): void {
if(value >= 0) {
console.log('Greater than zero')
}
}
The issue arises when the incoming variable has a value of null, as it will evaluate to truthy and execute the statement. Is there a more elegant solution to prevent this without adding additional checks?
One way to ensure that you are dealing with a number and not null is by using a type guard. This will make your code more accurate, as having `value: any` can lead to receiving a boolean or string:
public print(value: any): void {
if (typeof value === "number") {
//value is definitely a number and not null
if (value >= 0) {
console.log('Greater than zero')
}
}
}
This approach specifically confirms the input as a number before checking its value against zero. Therefore, null or non-number values will be excluded from further processing.
The type guard condition can also be condensed with the main logic for succinctness:
public print(value: any): void {
if (typeof value === "number" && value >= 0) {
console.log('Greater than zero')
}
}
Alternatively, you can extract the type guard check into a separate block to reduce nesting:
public print(value: any): void {
if (typeof value !== "number")
return;
//value is definitely a number and not null
if (value >= 0) {
console.log('Greater than zero')
}
}
Adding a null-check may be beneficial in this scenario.
You could also consider using number instead of any, but keep in mind that it will only work if strict null checks are enabled in your ts.conf.
function display(value: number): void {
if(value >= 0) {
console.log('Value is greater than zero')
}
}
display(null) // This code will not compile with strict null checks enabled
If your codebase prohibits the use of null, you can simply utilize undefined and perform an implicit conversion, as shown below:
public display(value: any): void {
if(value != undefined && value >= 0) {
console.log('Value is greater than zero')
}
}
This approach works because null == undefined (the double equals sign triggers a type conversion, while the triple equals sign does not).
When working with JavaScript, my go-to approach is usually:
`${value}` >= 0
// or
parseInt(value) >= 0
As for TypeScript, you can likely utilize the following:
public displayValue(value: any): void {
if (+`${value}` >= 0) {
console.log('Value is not less than zero')
}
}
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