Can mathematical operators *, /, +, -, ^ be used to convert a non-zero number to 1?

Use the expression n/n^0.

If n is not zero:

 Step    Explanation
------- -------------------------------------------------------------------------------
 n/n^0   Original expression.
 1^0     Any number divided by itself equals 1. Therefore n/n becomes 1.
 1       1 xor 0 equals 1.

If n is zero:

 Step    Explanation
------- -------------------------------------------------------------------------------
 n/n^0   Original expression.
 0/0^0   Since n is 0, n/n is 0/0.
 NaN^0   Zero divided by zero is mathematically undefined. Therefore 0/0 becomes NaN.
 0^0     In JavaScript, before any bitwise operation occurs, both operands are normalized.
         This means NaN becomes 0.
 0       0 xor 0 equals 0.

As you can see, all non-zero values get converted to 1, and 0 stays at 0. This leverages the fact that in JavaScript, NaN^0 is 0.

Demo:

[0, 1, 19575, -1].forEach(n => console.log(`${n} becomes ${n/n^0}.`))

c / (c + 5e-324) should work. (The constant 5e-324 is Number.MIN_VALUE, the smallest representable positive number.) If x is 0, that is exactly 0, and if x is nonzero (technically, if x is at least 4.45014771701440252e-308, which the smallest non-zero number allowed in the question, 0.01, is), JavaScript's floating-point math is too imprecise for the answer to be different than 1, so it will come out as exactly 1.

(((c/c)^c) - c) * (((c/c)^c) - c) will always return 1 for negatives and positives and 0 for 0.

It is definitely more confusing than the chosen answer and longer. However, I feel like it is less hacky and not relying on constants.

EDIT: As @JosephSible mentions, a more compact version of mine and @CRice's version which does not use constants is:

c/c^c-c