Conditionals and Logic
If Else Logic
Choose one of two branches with an if/else statement.
if-else
An `if` statement runs its first branch when the condition is true. Otherwise, the `else` branch runs.
If Else Logic
if_else_logic.js
Replay: real traced execution (multi-file project)
const temperature = 72;
let label = "";
if (temperature >= 70) {
label = "warm";
} else {
label = "cool";
}
console.log("temperature=" + temperature);
console.log("label=" + label);
const temperature = 55;
let label = "";
if (temperature >= 70) {
label = "warm";
} else {
label = "cool";
}
console.log("temperature=" + temperature);
console.log("label=" + label);
const temperature = 90;
let label = "";
if (temperature >= 70) {
label = "warm";
} else {
label = "cool";
}
console.log("temperature=" + temperature);
console.log("label=" + label);
temperature ← 72, label ← (empty)
1const temperature→ 72 = 72; //@temperature=55, 902let label→ (empty) = "";3if (temperature >= 70) {if (temperature >= 70)
1const temperature = 72; //@temperature=55, 902let label = "";3if (temperature72 >= 70) {4 label = "warm";5} else {console.log("temperature=" + temperature);
6 label = "cool";7}89console.log("temperature=" + temperature72);10console.log("label=" + labelwarm);outputtemperature=72 label=warm
temperature ← 55, label ← (empty)
1const temperature→ 55 = 55;2let label→ (empty) = "";3if (temperature >= 70) {console.log("temperature=" + temperature);
6 label = "cool";7}89console.log("temperature=" + temperature55);10console.log("label=" + labelcool);outputtemperature=55 label=cool
temperature ← 90, label ← (empty)
1const temperature→ 90 = 90;2let label→ (empty) = "";3if (temperature >= 70) {if (temperature >= 70)
1const temperature = 90;2let label = "";3if (temperature90 >= 70) {4 label = "warm";5} else {console.log("temperature=" + temperature);
6 label = "cool";7}89console.log("temperature=" + temperature90);10console.log("label=" + labelwarm);outputtemperature=90 label=warm