{{#if ...}}

{{#if expression}}...{{/if}}

{{#if expression}}...{{else if expression}}...{{/if}}

{{#if expression}}...{{else}}...{{/if}}

Conditional content can be wrapped in an if block.

const thingIsTrue = true;

<template>
  {{#if thingIsTrue}}
    Hello there!
  {{/if}}
</template>

Additionally more cases are possible with {{else if expression}} and a {{else}} clause for all other cases.

const waterTemperature = 38;
const isBoiling = (temperature) => temperature >= 100;
const isFreezing = (temperature) => temperature < 0;

<template>
  {{#if (isBoiling waterTemparature)}}
    Water is boiling
  {{else if (isFreezing waterTemperature)}}
    It's freezing - <i>brrr!</i>
  {{else}}
    Liquidity liquid
  {{/if}}
</template>

INFO

Just like in JavaScript, 0, false, null, undefined, and the empty string are falsy in Ember templates. Unlike in JavaScript, the empty array is also considered falsy in Ember templates.