Syntax support

[tanekim88]

Describe the problem

<script>
 const obj = getObject();
// obj can be { items: [1,2,3]}; or { items: undefined};
 const lookup = {
1: {
valid: true,
value:'good'
},
2:{
valid: true,
value:'bad'
},
3:{
valid: false,
value:'soso'
}
}
</script>
{#if obj.items}
     {#each obj.items as item}
// Here, I wish I could just do  {#each obj?.items as item}
// Instead of having to wrap with if block to
// check if obj.items is not undefined.
// Currently, it errors out if obj.items is null without the #if block

           {#if lookup[item].valid}
// Here I want to declare a variable:
// const lookupItem = lookup[item]; so that I can use 
//lookupItem.value instead of lookup[item].value in the body.
// Is there way to do so?
// I wish I could declare it when using if block
// {#if lookup[item] as lookupItem}
// or it would be also good if I could use local block like
// {# const lookupItem = lookup[item]; /}
                 <span>lookup[item].value</span>
           {/if}
     {/each}
{#if}

Currently, my attempt to use Svelte for my current project looks something like this (note that the complicated Array.from(...) equations could be avoided if there was a way to declare a variable inside the parent's each block and do calculations to get range value and store inside the variable.):

In Angular, there is a way to declare a variable through the if block,
https://angular.io/api/common/NgIf

I wish svelte could provide a solution like this.

Describe the proposed solution

I already described in the comments

Alternatives considered

I already described in the comments

Importance

would make my life easier

[bluwy]

Looks like you're requesting two features:

1. You want Svelte to auto-handle falsy values when itertaing with {#each}. Duplicate of Support falsy values being passed to #each to avoid an incidental conditional #1791
2. You want declare a variable inline in markup. Pending PR [feat] Implement RFC 33 - Constants in markup #6413

[tanekim88]

@bluwy Thanks! I will close this for now