console.log在求值之前/不求值时的表达式

Question

Given a statement such as let boolVal = 1 < 2 , is there a way to console log the actual expression, ie 1 < 2 not the true result?

 let boolVal = 1 < 2; console.log(boolVal) // logs out the boolean result console.log(boolVal.toString()) // logs out the boolean result as a string /* is there a way to get just '1 < 2' itself to be logged out? */ 

Answer 1

You can achieve this by making a custom function:

 function printExpression(x,y){ console.log( (x<y?x:y) + " < " + (x<y?y:x)); } printExpression(1,2); printExpression(4,3); 

Answer 2

You could make a function that makes the comparison, and log both the result of that function and the function itself.

 function boolValComparer(val1, val2) { console.log(val1, '<', val2); // logs the boolean comparison as string with parameters return val1 < val2; } let boolVal = boolValComparer(1, 2); console.log(boolVal) // logs out the boolean result console.log(boolValComparer) // logs out the comparer function as a string 

Answer 3

let boolVal = 1 < 2;

You cant log 1 < 2 directly because they are compared and stored in boolVal. What you can do is a workaround.

Store 1 and 2 in variables var1 and var2.

let boolVal = var1 < var2

if boolVal:
    console.log(var1 + "<" + var2)
else:
    console.log(var1 + ">" + var2)

Answer 4

From your response in the comment section, I see you need a generic solution with different operands. The simplest solution I can think of is by using eval.

1- Create an array of strings array[]. You could creare a string. "" +expression. 2- console.log(array[index]+ eval(array[index]) )

Although i would not recommend. Eval is bad for both performance and security. Another workaround is to make a connection for the results and for string you create from the first step. Like 2 arrays or create objects with 2 attributes. {value:, expression}. You can print them accourdingly when you print the variable.